aiohttp's ClientSession is vulnerable to CRLF injection via method

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS 4.0

6.9 · 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 · score source

EPSS

• CVE-2023-49082: 0.95% estimated exploitation activity in the next 30 days; percentile 61.22 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Improper validation makes it possible for an attacker to modify the HTTP request (e.g. insert a new header) or even create a new HTTP request if the attacker controls the HTTP method. Details The vulnerability occurs only if the attacker can control the HTTP method (GET, POST etc.) of the request. Previous releases performed no validation on the provided value. If an attacker controls the HTTP method it will be used as is and can lead to HTTP request smuggling. PoC A minimal example can be found here: https://gist.github.com/jnovikov/7f411ae9fe6a9a7804cf162a3bdbb44b Impact If the attacker can control the HTTP version of the request it will be able to modify the request (request smuggling). Workaround If unable to upgrade and using user-provided values for the request method, perform manual validation of the user value (e.g. by restricting it to a few known values like GET, POST etc.). Patch: https://github.com/aio-libs/aiohttp/pull/7806/files

Published by the source

27 Nov 2023, 23:17 UTC

Last modified by the source

10 Sep 2026, 03:49 UTC

Source last checked

26 Oct 2026, 13:35 UTC

1. Revision 3 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-qvrw-v9rv-5rjx

2. Revision 2 · amended · 25 Oct 2026

   Reviewed OSV alias/range/CVSS4 correction; package source scopes and original publication preserved. No customer finding resolved.

3. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-qvrw-v9rv-5rjx

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# Patch Next advisory brief: CVE-2023-49082

Advisory: aiohttp's ClientSession is vulnerable to CRLF injection via method
IDs: CVE-2023-49082, GHSA-qvrw-v9rv-5rjx
Record: https://patchnext.com/advisories/cve-2023-49082 (revision 3, source checked 26 Oct 2026, 13:35 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 6.9)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: aiohttp 3.9.0. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI aiohttp: affected < 3.9.0; fixed in 3.9.0

## Suggested inspection (read-only)
- `python -m pip show aiohttp`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on aiohttp.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-qvrw-v9rv-5rjx (OSV record GHSA-qvrw-v9rv-5rjx lists affected ranges: PyPI aiohttp >=0 <3.9.0 (fixed))
- Verified: https://github.com/advisories/GHSA-qvrw-v9rv-5rjx (GitHub-reviewed advisory GHSA-qvrw-v9rv-5rjx lists affected ranges: PyPI aiohttp >=0 <3.9.0)

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