aiohttp: CRLF injection in multipart headers

Answer in brief

CVE-2026-50269 records a High severity (CVSS 7.5) vulnerability in aiohttp: CRLF injection in multipart headers. The current sources do not mark it as known exploited. The current feed maps aiohttp (pip), aiohttp (pypi). Check affected ranges and fixed versions before updating.

Analysis pending evidence review

HOL Guard separates source facts from reviewed analysis. See the methodology.

Published Jun 15, 2026Updated Sep 10, 2026Source checked Sep 17, 2026First seen by HOL Jun 19, 2026Material review Sep 10, 2026

Upstream Advisory

Key facts

Risk: High · CVSS 7.5
Exploitation: Not marked as known exploited
Affected software: 2 mapped packages or products
Fix availability: Available

Why this deserves its current priority

CVSS is 7.5. The current sources do not mark it as known exploited. Treat this as a source-backed prioritization signal, not a statement about your environment.

Analysis status

Analysis pending evidence review

Factual feed record only; HOL analysis is not approved for indexing. Read the methodology.

Affected scope and exposure questions

The current feed maps aiohttp (pip), aiohttp (pypi). Check affected ranges and fixed versions before updating.

Mapped affected packages and fixed versions
Package	Affected range	Fixed version
aiohttppip	<=3.13.5	3.14.0
aiohttppypi	>=0 <3.14.0	3.14.0

Recommended response

Check inventory. Check lockfiles and deployed manifests for aiohttp, aiohttp.
Review the reported fix. Update aiohttp to 3.14.0; aiohttp to 3.14.0 if you use the affected versions. Test the change in a non-production environment first.

Evidence timeline and material changes

Published upstream
Jun 15, 2026
Evidence: source:osv:source_dates:source-dates:record
Source modified
Sep 10, 2026
Evidence: source:osv:source_dates:source-dates:record
First seen by HOL
Jun 19, 2026

Sources and claim methodology

Upstream source 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

Quoted source text, attributed separately from HOL analysis.