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Advisory details: vulnrichment / CVE-2026-59921
Advisory ID vulnrichment/CVE-2026-59921
Aliases
Summary Netty is an asynchronous, event-driven network application framework. Prior to versions 4.1.136.Final and 4.2.16.Final, HttpPostRequestEncoder constructs multipart HTTP request bodies by directly concatenating user-supplied filenames and field names into Content-Disposition MIME headers without validating or sanitizing CRLF characters (\r\n). Since MIME headers are delimited by CRLF, an attacker who controls the filename can inject arbitrary MIME headers into the multipart body part. The root cause is that neither the encoder nor the FileUpload implementations' setFilename() methods, which only check for null, neutralize CRLF characters before the filename is embedded into the header. This issue has been fixed in versions 4.1.136.Final and 4.2.16.Final.
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 (1)
CWE-93 Improper Neutralization of CRLF Sequences ('CRLF Injection')
System Score Found at
cvssv3.1 5.7
ssvc Track
Reference id Reference type URL
https://github.com/netty/netty/security/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 None
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/ Found at 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'}]