Staging Environment: Content and features may be unstable or change without notice.
Advisory details: gitlab / maven/io.netty/netty-codec-http/CVE-2026-59921
Advisory ID gitlab/maven/io.netty/netty-codec-http/CVE-2026-59921
Aliases CVE-2026-59921
GHSA-gcjf-9mgh-3p7g
Summary Netty: CRLF Injection via Multipart Filename in Netty HttpPostRequestEncoder | Field | Value | |-------|-------| | **Product** | Netty | | **Version** | 4.2.12.Final (and all prior versions with codec-http multipart) | | **Component** | `io.netty.handler.codec.http.multipart.HttpPostRequestEncoder` | | **Vulnerability Type** | CWE-93: Improper Neutralization of CRLF Sequences / CWE-113: HTTP Response Splitting | | **Impact** | MIME Header Injection / Content-Type Spoofing / XSS via Content-Disposition | | **CVSS 3.1 Score** | **8.1 (High)** | | **CVSS 3.1 Vector** | `CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N` | | **Attack Vector** | Network | | **Attack Complexity** | Low | | **Privileges Required** | Low (attacker must be able to upload files with controlled filenames) | | **User Interaction** | None | | **Scope** | Unchanged | | **Confidentiality Impact** | High | | **Integrity Impact** | High | | **Availability Impact** | None |
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-93 Improper Neutralization of CRLF Sequences ('CRLF Injection')
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-http/CVE-2026-59921.yml
Reference id Reference type URL
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-gcjf-9mgh-3p7g
CVE-2026-59921 https://nvd.nist.gov/vuln/detail/CVE-2026-59921
GHSA-gcjf-9mgh-3p7g https://github.com/advisories/GHSA-gcjf-9mgh-3p7g
No exploits are available.

No EPSS data available for this advisory.

Patch URL
There are no known patches.
Vector: CVSS:3.1/AV:A/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N Found at https://gitlab.com/gitlab-org/advisories-community/-/blob/main/maven/io.netty/netty-codec-http/CVE-2026-59921.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:N/T:P/P:M/B:A/M:M/D:T/2026-07-29T12:49:35Z/

Decision: Track

Source URL: https://github.com/cisagov/vulnrichment/blob/develop/2026/59xxx/CVE-2026-59921.json

Source Advisory: vulnrichment/CVE-2026-59921

View SSVC decision tree 
[{'Exploitation': 'poc'},
 {'Automatable': 'no'},
 {'Technical Impact': 'partial'},
 {'Mission Prevalence': 'minimal'},
 {'Public Well-being Impact': 'material'},
 {'Mission & Well-being': 'medium'}]