CVE-2026-69244: AIOHTTP: Out-of-bounds heap read in C HTTP response parser error path (malformed chunked response)

Severity: high (CVSS 7.1 v4.0)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.5% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-08-03 · updated 2026-10-23
Weakness: CWE-125

Description

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.3, an out-of-bounds heap read could occur in the C response parser while building an error message for a malformed response. An attacker controlled server, or possibly an accidental response, could trigger a DoS in the client. The vulnerable path was error message construction in aiohttp/_http_parser.pyx, where an llhttp error-position pointer was used to build a snippet for malformed chunked responses and malformed request or response bytes at the buffer end. This issue is fixed in version 3.14.3.

Affected products

Pypi Aiohttp: before 3.14.3; 0.1, 0.10.0, 0.10.1, 0.10.2, 0.11.0, 0.12.0 (+303) — fixed in 3.14.3
aio-libs aiohttp: before 3.14.3

How to fix

Upgrade to a fixed version: Pypi Aiohttp 3.14.3. Check the vendor advisory for mitigations.

References

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