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Advisory details: gitlab / maven/io.netty/netty-codec-http2/CVE-2026-56819
Advisory ID gitlab/maven/io.netty/netty-codec-http2/CVE-2026-56819
Aliases CVE-2026-56819
GHSA-93wv-jw9v-4972
Summary Netty: HTTP/2 decompression leaks ByteBuf reference count when the decompressor channel is already closed (Direct memory leak / OOM DoS) A remote, unauthenticated peer can leak one direct `ByteBuf` per HTTP/2 `DATA` frame in applications that enable HTTP/2 content decompression via `DelegatingDecompressorFrameListener`. When a `DATA` frame is processed for a stream whose decompressor has already been closed, `Http2Decompressor.decompress(...)` retains the frame buffer but never releases it on the error path, so its reference count never returns to zero. Repeating this over a long-lived HTTP/2 connection exhausts direct memory and crashes the JVM with `OutOfMemoryError` — a denial of service.
Status Published
Exploitability 0.5
Weighted Severity 0.0
Risk
Affected and Fixed Packages Package Details
Introduced and Fixed Package Commit Patches Package Commit Patches Details
Weaknesses (3)
CWE-400 Uncontrolled Resource Consumption
CWE-937 OWASP Top Ten 2013 Category A9 - Using Components with Known Vulnerabilities
CWE-1035 OWASP Top Ten 2017 Category A9 - Using Components with Known Vulnerabilities
System Score Found at
cvssv3.1 https://gitlab.com/gitlab-org/advisories-community/-/blob/main/maven/io.netty/netty-codec-http2/CVE-2026-56819.yml
Reference id Reference type URL
https://github.com/netty/netty/commit/5b68c61f37aa4a3045cba624cbea239655c9003b
https://github.com/netty/netty/commit/bb2ff68a1fb71cb4b0eb9a9e17b66c52aff680c6
https://github.com/netty/netty/releases/tag/netty-4.1.136.Final
https://github.com/netty/netty/releases/tag/netty-4.2.16.Final
https://github.com/netty/netty/security/advisories/GHSA-93wv-jw9v-4972
CVE-2026-56819 https://nvd.nist.gov/vuln/detail/CVE-2026-56819
GHSA-93wv-jw9v-4972 https://github.com/advisories/GHSA-93wv-jw9v-4972
No exploits are available.

No EPSS data available for this advisory.

Patch URL
There are no known patches.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Found at https://gitlab.com/gitlab-org/advisories-community/-/blob/main/maven/io.netty/netty-codec-http2/CVE-2026-56819.yml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none

Vector: SSVCv2/E:P/A:Y/T:P/P:M/B:A/M:M/D:T/2026-07-23T13:55:20Z/

Decision: Track

Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2026/56xxx/CVE-2026-56819.json

Source Advisory: vulnrichment/CVE-2026-56819

View SSVC decision tree 
[{'Exploitation': 'poc'},
 {'Automatable': 'yes'},
 {'Technical Impact': 'partial'},
 {'Mission Prevalence': 'minimal'},
 {'Public Well-being Impact': 'material'},
 {'Mission & Well-being': 'medium'}]