aiohttp: CRLF injection in multipart headers

CVE-2026-50269 → View on GitHub ↗ View on CVE.org ↗ View on NVD ↗

Description

Summary

Attacker-controlled input included into multipart/payload headers can be used to modify a request to inject additional headers or similar.

Impact

In the unlikely situation that an application is passing user-controlled strings into MultipartWriter.append(headers=...) or Payload.headers, then an attacker may be able to modify the request to inject headers or change the contents of the request.

Workaround

Sanitise such user input.

Patch: https://github.com/aio-libs/aiohttp/commit/bf88077ebb14f4c29924b8e8904cba20c55c28b8

Basic information

Type
reviewed
Severity
low
Advisory on GitHub
Open advisory ↗
Repository advisory
Open repository advisory ↗
Source code
Browse source ↗
Published (advisory)
2026-06-15 20:07:26 UTC
Updated
2026-06-15 20:07:27 UTC
GitHub reviewed
2026-06-15 20:07:26 UTC

EPSS Score

Score Percentile
0.04% 11.67%

CVSS Scores

Base score Version Severity Vector
2.7 4.0 —
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:L/VA:N/SC:N/SI:N/SA:N/E:U Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network.
Attack complexity (AC:L)
Exploitation conditions are straightforward and stable.
Attack requirements (AT:N)
No additional preconditions are required beyond normal reachability.
Privileges required (PR:N)
No privileges are required.
User interaction (UI:N)
No user interaction is required.
Vulnerable system confidentiality impact (VC:N)
No confidentiality impact on the vulnerable system.
Vulnerable system integrity impact (VI:L)
Limited integrity impact on the vulnerable system.
Vulnerable system availability impact (VA:N)
No availability impact on the vulnerable system.
Subsequent system confidentiality impact (SC:N)
No confidentiality impact on subsequent systems.
Subsequent system integrity impact (SI:N)
No integrity impact on subsequent systems.
Subsequent system availability impact (SA:N)
No availability impact on subsequent systems.
Exploit maturity (threat) (E:U)
Unreported: no public PoC, no reported exploitation, and no known simplification tools.

Identifiers

Type Value
GHSA GHSA-m6qw-4cw2-hm4m ↗
CVE CVE-2026-50269 ↗

CWEs

CWE id Name
CWE-93 Improper Neutralization of CRLF Sequences ('CRLF Injection')
CWE-113 Improper Neutralization of CRLF Sequences in HTTP Headers ('HTTP Request/Response Splitting')

Credits

  • tonghuaroot (reporter)
  • Dreamsorcerer (remediation_developer)

Affected packages (1)

Vulnerable version ranges and first patched releases as published by GitHub.

Ecosystem Package Vulnerable range First patched Vulnerable functions
pip aiohttp <= 3.13.5 3.14.0 —

References

cvelogic Threat Intelligence