What is CVE-2026-54277?

CVE-2026-54277 is a high-severity vulnerability in Aiohttp, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2026-06-22.

How severe is CVE-2026-54277?

High severity. CVSS v3 base score is 7.5 out of 10.

Resource exhaustion in Aiohttp

CVE-2026-54277

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.1, it is possible to bypass the max_line_size check in parts of an HTTP request in the C parser. If using the optimised C parser (the default in pre-built wheels), then an attacker may be able to send oversized lines through the HTTP parser and use an excessive amount of memory, potentially leading to DoS. This vulnerability is fixed in 3.14.1.

Published 2026-06-22 · last modified 2026-06-30.

CVSS v3 metric

CVSS v3 base score 7.5 (High). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H.

EPSS exploit prediction

EPSS: 0.006 (44.6th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 45th percentile — 44.6% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.003 · newest: 0.006 · change: +0.002

Affected products

Aiohttp
Aio-Libs Aiohttp — versions < 3.14.1

Weakness classification (CWE)

CWE-770 — Allocation of Resources Without Limits or Throttling

References

github.com/aio-libs/aiohttp/security/advisories/GHSA-63hw-fmq6-xxg2 (Vendor Advisory)
github.com/aio-libs/aiohttp/commit/5ab61bb4cd88f19b712f12c7c9295fe262bf804d (Patch)

Frequently asked questions

What is CVE-2026-54277?: CVE-2026-54277 is a high-severity vulnerability in Aiohttp, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2026-06-22.
How severe is CVE-2026-54277?: High severity. CVSS v3 base score is 7.5 out of 10.