Package Instance
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GET /api/packages/68028?format=api
{ "url": "http://public2.vulnerablecode.io/api/packages/68028?format=api", "purl": "pkg:maven/io.netty/netty-codec-http2@4.1.132.Final", "type": "maven", "namespace": "io.netty", "name": "netty-codec-http2", "version": "4.1.132.Final", "qualifiers": {}, "subpath": "", "is_vulnerable": true, "next_non_vulnerable_version": "4.1.133.Final", "latest_non_vulnerable_version": "4.2.13.Final", "affected_by_vulnerabilities": [ { "url": "http://public2.vulnerablecode.io/api/vulnerabilities/356829?format=api", "vulnerability_id": "VCID-7rcj-a9zf-yfhb", "summary": "Netty: HttpContentDecompressor maxAllocation bypass when Content-Encoding set to br/zstd/snappy leads to decompression bomb DoS\n## Summary\n\n`HttpContentDecompressor` accepts a `maxAllocation` parameter to limit decompression buffer size and prevent decompression bomb attacks. This limit is correctly enforced for gzip and deflate encodings via `ZlibDecoder`, but is silently ignored when the content encoding is `br` (Brotli), `zstd`, or `snappy`. An attacker can bypass the configured decompression limit by sending a compressed payload with `Content-Encoding: br` instead of `Content-Encoding: gzip`, causing unbounded memory allocation and out-of-memory denial of service.\n\nThe same vulnerability exists in `DelegatingDecompressorFrameListener` for HTTP/2 connections.\n\n## Details\n\n`HttpContentDecompressor` stores the `maxAllocation` value at construction time (`HttpContentDecompressor.java:89`) and uses it in `newContentDecoder()` to create the appropriate decompression handler.\n\nFor gzip/deflate, `maxAllocation` is forwarded to `ZlibCodecFactory.newZlibDecoder()`:\n\n```java\n// HttpContentDecompressor.java:101 — maxAllocation IS enforced\n.handlers(ZlibCodecFactory.newZlibDecoder(ZlibWrapper.GZIP, maxAllocation))\n```\n\n`ZlibDecoder.prepareDecompressBuffer()` enforces this as a hard cap by setting the buffer's `maxCapacity` and throwing `DecompressionException` when the limit is reached:\n\n```java\n// ZlibDecoder.java:68 — hard limit on buffer capacity\nreturn ctx.alloc().heapBuffer(Math.min(preferredSize, maxAllocation), maxAllocation);\n// ZlibDecoder.java:80 — throws when exceeded\nthrow new DecompressionException(\"Decompression buffer has reached maximum size: \" + buffer.maxCapacity());\n```\n\nFor brotli, zstd, and snappy, the decoders are created without any size limit:\n\n```java\n// HttpContentDecompressor.java:120 — maxAllocation IGNORED\n.handlers(new BrotliDecoder())\n\n// HttpContentDecompressor.java:129 — maxAllocation IGNORED\n.handlers(new SnappyFrameDecoder())\n\n// HttpContentDecompressor.java:138 — maxAllocation IGNORED\n.handlers(new ZstdDecoder())\n```\n\n`BrotliDecoder` has no `maxAllocation` parameter at all — there is no way to constrain its output. It streams decompressed data in chunks via `fireChannelRead` with no total limit.\n\n`ZstdDecoder()` defaults to a 4MB `maximumAllocationSize`, but this only constrains individual buffer allocations, not total output. The decode loop (`ZstdDecoder.java:100-114`) creates new buffers and fires `channelRead` repeatedly, so total decompressed output is unbounded.\n\nThe identical pattern exists in `DelegatingDecompressorFrameListener.newContentDecompressor()` at lines 188-210 for HTTP/2.\n\n## PoC\n\n1. Configure a Netty HTTP server with decompression bomb protection:\n\n```java\npipeline.addLast(new HttpContentDecompressor(1048576)); // 1MB max\npipeline.addLast(new HttpObjectAggregator(1048576)); // 1MB max\n```\n\n2. Generate a brotli-compressed bomb (~1KB compressed → 1GB decompressed):\n\n```python\nimport brotli\nbomb = b'\\x00' * (1024 * 1024 * 1024) # 1GB of zeros\ncompressed = brotli.compress(bomb, quality=11)\nwith open('bomb.br', 'wb') as f:\n f.write(compressed)\n# compressed size: ~1KB\n```\n\n3. Send the bomb with gzip encoding (BLOCKED by maxAllocation):\n\n```bash\n# This is caught — ZlibDecoder enforces the 1MB limit\ncurl -X POST http://target:8080/api \\\n -H 'Content-Encoding: gzip' \\\n --data-binary @bomb.gz\n# Result: DecompressionException thrown at 1MB\n```\n\n4. Send the same bomb with brotli encoding (BYPASSES maxAllocation):\n\n```bash\n# This bypasses the limit — BrotliDecoder has no maxAllocation\ncurl -X POST http://target:8080/api \\\n -H 'Content-Encoding: br' \\\n --data-binary @bomb.br\n# Result: Full 1GB decompressed into memory → OOM\n```\n\n5. The same bypass works with `Content-Encoding: zstd` and `Content-Encoding: snappy`.\n\n## Impact\n\n- **Denial of Service**: An attacker can cause out-of-memory conditions on any Netty server that relies on `maxAllocation` for decompression bomb protection, by simply using a non-gzip content encoding.\n- **False sense of security**: Developers who explicitly configure `maxAllocation` to protect against decompression bombs are not actually protected for brotli, zstd, or snappy encodings. The API documentation implies all encodings are covered.\n- **Trivial bypass**: The attacker only needs to change one HTTP header (`Content-Encoding: br` instead of `Content-Encoding: gzip`) to circumvent the protection entirely.\n- **Both HTTP/1.1 and HTTP/2**: The vulnerability exists in both `HttpContentDecompressor` (HTTP/1.1) and `DelegatingDecompressorFrameListener` (HTTP/2).\n\n## Recommended Fix\n\nPass `maxAllocation` to all decoder constructors. For `BrotliDecoder`, which currently has no `maxAllocation` support, add the parameter:\n\n**HttpContentDecompressor.java** — pass maxAllocation to all decoders:\n\n```java\n// Line 120: BrotliDecoder — add maxAllocation support\n.handlers(new BrotliDecoder(maxAllocation))\n\n// Line 129: SnappyFrameDecoder — add maxAllocation support\n.handlers(new SnappyFrameDecoder(maxAllocation))\n\n// Line 138: ZstdDecoder — forward the configured maxAllocation\n.handlers(new ZstdDecoder(maxAllocation))\n```\n\n**DelegatingDecompressorFrameListener.java** — same fix at lines 188-210.\n\n**BrotliDecoder** — add `maxAllocation` parameter with the same semantics as `ZlibDecoder.prepareDecompressBuffer()`: set buffer maxCapacity and throw `DecompressionException` when the total decompressed output exceeds the limit.\n\n**SnappyFrameDecoder** — add `maxAllocation` parameter with equivalent enforcement.\n\n**ZstdDecoder** — ensure that when `maxAllocation` is set, total output across all buffers is bounded (not just per-buffer allocation size).", "references": [ { "reference_url": "https://github.com/netty/netty", "reference_id": "", "reference_type": "", "scores": [ { "value": "7.5", "scoring_system": "cvssv3.1", "scoring_elements": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H" }, { "value": "HIGH", "scoring_system": "generic_textual", "scoring_elements": "" } ], "url": "https://github.com/netty/netty" }, { "reference_url": "https://github.com/netty/netty/security/advisories/GHSA-f6hv-jmp6-3vwv", "reference_id": "", "reference_type": "", "scores": [ { "value": "7.5", "scoring_system": "cvssv3.1", "scoring_elements": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H" }, { "value": "HIGH", "scoring_system": "cvssv3.1_qr", "scoring_elements": "" }, { "value": "HIGH", "scoring_system": "generic_textual", "scoring_elements": "" } ], "url": "https://github.com/netty/netty/security/advisories/GHSA-f6hv-jmp6-3vwv" }, { "reference_url": "https://github.com/advisories/GHSA-f6hv-jmp6-3vwv", "reference_id": "GHSA-f6hv-jmp6-3vwv", "reference_type": "", "scores": [ { "value": "HIGH", "scoring_system": "cvssv3.1_qr", "scoring_elements": "" } ], "url": "https://github.com/advisories/GHSA-f6hv-jmp6-3vwv" } ], "fixed_packages": [ { "url": "http://public2.vulnerablecode.io/api/packages/1103437?format=api", "purl": "pkg:maven/io.netty/netty-codec-http2@4.1.133.Final", "is_vulnerable": false, "affected_by_vulnerabilities": [], "resource_url": "http://public2.vulnerablecode.io/packages/pkg:maven/io.netty/netty-codec-http2@4.1.133.Final" }, { "url": "http://public2.vulnerablecode.io/api/packages/1103436?format=api", "purl": "pkg:maven/io.netty/netty-codec-http2@4.2.13.Final", "is_vulnerable": false, "affected_by_vulnerabilities": [], "resource_url": "http://public2.vulnerablecode.io/packages/pkg:maven/io.netty/netty-codec-http2@4.2.13.Final" } ], "aliases": [ "CVE-2026-42587", "GHSA-f6hv-jmp6-3vwv" ], "risk_score": 4.0, "exploitability": "0.5", "weighted_severity": "8.0", "resource_url": "http://public2.vulnerablecode.io/vulnerabilities/VCID-7rcj-a9zf-yfhb" } ], "fixing_vulnerabilities": [ { "url": "http://public2.vulnerablecode.io/api/vulnerabilities/24792?format=api", "vulnerability_id": "VCID-cs79-xzk6-4kgp", "summary": "Netty HTTP/2 CONTINUATION Frame Flood DoS via Zero-Byte Frame Bypass\n### Summary\nA remote user can trigger a Denial of Service (DoS) against a Netty HTTP/2 server by sending a flood of `CONTINUATION` frames. The server's lack of a limit on the number of `CONTINUATION` frames, combined with a bypass of existing size-based mitigations using zero-byte frames, allows an user to cause excessive CPU consumption with minimal bandwidth, rendering the server unresponsive.\n\n### Details\nThe vulnerability exists in Netty's `DefaultHttp2FrameReader`. When an HTTP/2 `HEADERS` frame is received without the `END_HEADERS` flag, the server expects one or more subsequent `CONTINUATION` frames. However, the implementation does not enforce a limit on the *count* of these `CONTINUATION` frames.\n\nThe key issue is located in `codec-http2/src/main/java/io/netty/handler/codec/http2/DefaultHttp2FrameReader.java`. The `verifyContinuationFrame()` method checks for stream association but fails to implement a frame count limit.\n\nAny user can exploit this by sending a stream of `CONTINUATION` frames with a zero-byte payload. While Netty has a `maxHeaderListSize` protection to limit the total size of headers, this check is never triggered by zero-byte frames. The logic effectively evaluates to `maxHeaderListSize - 0 < currentSize`, which will not trigger the limit until a non-zero byte is added. As a result, the server is forced to process an unlimited number of frames, consuming a CPU thread and monopolizing the connection.\n\n`codec-http2/src/main/java/io/netty/handler/codec/http2/DefaultHttp2FrameReader.java`\n\n**`verifyContinuationFrame()` (lines 381-393)** — No frame count check:\n```java\nprivate void verifyContinuationFrame() throws Http2Exception {\n verifyAssociatedWithAStream();\n if (headersContinuation == null) {\n throw connectionError(PROTOCOL_ERROR, \"...\");\n }\n if (streamId != headersContinuation.getStreamId()) {\n throw connectionError(PROTOCOL_ERROR, \"...\");\n }\n // NO frame count limit!\n}\n```\n\n**`HeadersBlockBuilder.addFragment()` (lines 695-723)** — Byte limit bypassed by 0-byte frames:\n```java\n// Line 710-711: This check NEVER fires when len=0\nif (headersDecoder.configuration().maxHeaderListSizeGoAway() - len <\n headerBlock.readableBytes()) {\n headerSizeExceeded(); // 10240 - 0 < 1 => FALSE always\n}\n```\n\nWhen `len=0`: `maxGoAway - 0 < readableBytes` → `10240 < 1` → FALSE. The byte limit is never triggered.\n\n### Impact\nThis is a CPU-based Denial of Service (DoS). Any service using Netty's default HTTP/2 server implementation is impacted. An unauthenticated user can exhaust server CPU resources and block legitimate users, leading to service unavailability. The low bandwidth requirement for the attack makes it highly practical.", "references": [ { "reference_url": "https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2026-33871.json", "reference_id": "", "reference_type": "", "scores": [ { "value": "7.5", "scoring_system": "cvssv3", "scoring_elements": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H" } ], "url": "https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2026-33871.json" }, { "reference_url": "https://api.first.org/data/v1/epss?cve=CVE-2026-33871", "reference_id": "", "reference_type": "", "scores": [ { "value": "0.00025", "scoring_system": "epss", "scoring_elements": "0.0707", "published_at": "2026-04-26T12:55:00Z" }, { "value": "0.00025", "scoring_system": "epss", "scoring_elements": "0.07065", "published_at": "2026-04-24T12:55:00Z" }, { "value": "0.00025", "scoring_system": "epss", "scoring_elements": "0.0708", "published_at": "2026-04-21T12:55:00Z" }, { "value": "0.00028", "scoring_system": "epss", "scoring_elements": "0.07759", "published_at": "2026-04-29T12:55:00Z" }, { "value": "0.00037", "scoring_system": "epss", "scoring_elements": "0.10692", "published_at": "2026-05-05T12:55:00Z" }, { "value": "0.00037", "scoring_system": "epss", "scoring_elements": "0.10826", "published_at": "2026-05-07T12:55:00Z" }, { "value": "0.00081", "scoring_system": "epss", "scoring_elements": "0.23856", "published_at": "2026-04-07T12:55:00Z" }, { "value": "0.00081", "scoring_system": "epss", "scoring_elements": "0.24035", "published_at": "2026-04-02T12:55:00Z" }, { "value": "0.00081", "scoring_system": "epss", "scoring_elements": "0.24074", "published_at": "2026-04-04T12:55:00Z" }, { "value": "0.00081", "scoring_system": "epss", "scoring_elements": "0.23923", "published_at": "2026-04-08T12:55:00Z" }, { "value": "0.00081", "scoring_system": "epss", "scoring_elements": "0.23969", "published_at": "2026-04-09T12:55:00Z" }, { "value": "0.00081", "scoring_system": "epss", "scoring_elements": "0.23986", "published_at": "2026-04-11T12:55:00Z" }, { "value": "0.00081", "scoring_system": "epss", "scoring_elements": "0.23942", "published_at": "2026-04-12T12:55:00Z" }, { "value": "0.00081", "scoring_system": "epss", "scoring_elements": "0.23885", "published_at": "2026-04-13T12:55:00Z" }, { "value": "0.00081", "scoring_system": "epss", "scoring_elements": "0.23896", "published_at": "2026-04-16T12:55:00Z" }, { "value": "0.00081", "scoring_system": "epss", "scoring_elements": "0.23886", "published_at": "2026-04-18T12:55:00Z" } ], "url": "https://api.first.org/data/v1/epss?cve=CVE-2026-33871" }, { "reference_url": "https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-33871", "reference_id": "", "reference_type": "", "scores": [], "url": "https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-33871" }, { "reference_url": "https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml", "reference_id": "", "reference_type": "", "scores": [ { "value": "5.9", "scoring_system": "cvssv3.1", "scoring_elements": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:N/A:H" } ], "url": "https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml" }, { "reference_url": "https://github.com/netty/netty", "reference_id": "", "reference_type": "", "scores": [ { "value": "8.7", "scoring_system": "cvssv4", "scoring_elements": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N" }, { "value": "HIGH", "scoring_system": "generic_textual", "scoring_elements": "" } ], "url": "https://github.com/netty/netty" }, { "reference_url": "https://github.com/netty/netty/security/advisories/GHSA-w9fj-cfpg-grvv", "reference_id": "", "reference_type": "", "scores": [ { "value": "HIGH", "scoring_system": "cvssv3.1_qr", "scoring_elements": "" }, { "value": "8.7", "scoring_system": "cvssv4", "scoring_elements": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N" }, { "value": "HIGH", "scoring_system": "generic_textual", "scoring_elements": "" }, { "value": "Track", "scoring_system": "ssvc", "scoring_elements": "SSVCv2/E:N/A:Y/T:P/P:M/B:A/M:M/D:T/2026-03-31T18:51:31Z/" } ], "url": "https://github.com/netty/netty/security/advisories/GHSA-w9fj-cfpg-grvv" }, { "reference_url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33871", "reference_id": "", "reference_type": "", "scores": [ { "value": "8.7", "scoring_system": "cvssv4", "scoring_elements": "CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N" }, { "value": "HIGH", "scoring_system": "generic_textual", "scoring_elements": "" } ], "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-33871" }, { "reference_url": "https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1132230", "reference_id": "1132230", "reference_type": "", "scores": [], "url": "https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=1132230" }, { "reference_url": "https://bugzilla.redhat.com/show_bug.cgi?id=2452456", "reference_id": "2452456", "reference_type": "", "scores": [], "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2452456" }, { "reference_url": "https://github.com/advisories/GHSA-w9fj-cfpg-grvv", "reference_id": "GHSA-w9fj-cfpg-grvv", "reference_type": "", "scores": [ { "value": "HIGH", "scoring_system": "cvssv3.1_qr", "scoring_elements": "" } ], "url": "https://github.com/advisories/GHSA-w9fj-cfpg-grvv" }, { "reference_url": "https://access.redhat.com/errata/RHSA-2026:10175", "reference_id": "RHSA-2026:10175", "reference_type": "", "scores": [], "url": "https://access.redhat.com/errata/RHSA-2026:10175" }, { "reference_url": "https://access.redhat.com/errata/RHSA-2026:10184", "reference_id": "RHSA-2026:10184", "reference_type": "", "scores": [], "url": "https://access.redhat.com/errata/RHSA-2026:10184" }, { "reference_url": "https://access.redhat.com/errata/RHSA-2026:13571", "reference_id": "RHSA-2026:13571", "reference_type": "", "scores": [], "url": "https://access.redhat.com/errata/RHSA-2026:13571" }, { "reference_url": "https://access.redhat.com/errata/RHSA-2026:14272", "reference_id": "RHSA-2026:14272", "reference_type": "", "scores": [], "url": "https://access.redhat.com/errata/RHSA-2026:14272" }, { "reference_url": "https://access.redhat.com/errata/RHSA-2026:14276", "reference_id": "RHSA-2026:14276", "reference_type": "", "scores": [], "url": "https://access.redhat.com/errata/RHSA-2026:14276" }, { "reference_url": "https://access.redhat.com/errata/RHSA-2026:7109", "reference_id": "RHSA-2026:7109", "reference_type": "", "scores": [], "url": "https://access.redhat.com/errata/RHSA-2026:7109" }, { "reference_url": "https://access.redhat.com/errata/RHSA-2026:7380", "reference_id": "RHSA-2026:7380", "reference_type": "", "scores": [], "url": "https://access.redhat.com/errata/RHSA-2026:7380" }, { "reference_url": "https://access.redhat.com/errata/RHSA-2026:8159", "reference_id": "RHSA-2026:8159", "reference_type": "", "scores": [], "url": "https://access.redhat.com/errata/RHSA-2026:8159" }, { "reference_url": "https://access.redhat.com/errata/RHSA-2026:8509", "reference_id": "RHSA-2026:8509", "reference_type": "", "scores": [], "url": "https://access.redhat.com/errata/RHSA-2026:8509" } ], "fixed_packages": [ { "url": "http://public2.vulnerablecode.io/api/packages/68028?format=api", "purl": "pkg:maven/io.netty/netty-codec-http2@4.1.132.Final", "is_vulnerable": true, "affected_by_vulnerabilities": [ { "vulnerability": "VCID-7rcj-a9zf-yfhb" } ], "resource_url": "http://public2.vulnerablecode.io/packages/pkg:maven/io.netty/netty-codec-http2@4.1.132.Final" }, { "url": "http://public2.vulnerablecode.io/api/packages/68029?format=api", "purl": "pkg:maven/io.netty/netty-codec-http2@4.2.11.Final", "is_vulnerable": false, "affected_by_vulnerabilities": [], "resource_url": "http://public2.vulnerablecode.io/packages/pkg:maven/io.netty/netty-codec-http2@4.2.11.Final" } ], "aliases": [ "CVE-2026-33871", "GHSA-w9fj-cfpg-grvv" ], "risk_score": 4.0, "exploitability": "0.5", "weighted_severity": "8.0", "resource_url": "http://public2.vulnerablecode.io/vulnerabilities/VCID-cs79-xzk6-4kgp" } ], "risk_score": "4.0", "resource_url": "http://public2.vulnerablecode.io/packages/pkg:maven/io.netty/netty-codec-http2@4.1.132.Final" }