What is CVE-2026-34513?

CVE-2026-34513 is a high-severity vulnerability in Aiohttp, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2026-04-01.

How severe is CVE-2026-34513?

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

Resource exhaustion in Aiohttp

CVE-2026-34513

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to version 3.13.4, an unbounded DNS cache could result in excessive memory usage possibly resulting in a DoS situation. This issue has been patched in version 3.13.4.

Published 2026-04-01 · last modified 2026-06-17.

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 (47.1th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 47th percentile — 47.1% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.004 · newest: 0.006 · change: +0.002

Affected products

Aiohttp
Aio-Libs Aiohttp — versions < 3.13.4

Weakness classification (CWE)

CWE-770 — Allocation of Resources Without Limits or Throttling

References

github.com/aio-libs/aiohttp/security/advisories/GHSA-hcc4-c3v8-rx92 (Patch, Vendor Advisory)
github.com/aio-libs/aiohttp/commit/c4d77c3533122be353b8afca8e8675e3b4cbda98 (Patch)
github.com/aio-libs/aiohttp/releases/tag/v3.13.4 (Release Notes)

Frequently asked questions

What is CVE-2026-34513?: CVE-2026-34513 is a high-severity vulnerability in Aiohttp, classified under Allocation of Resources Without Limits or Throttling. CVSS score: 7.5/10. Published 2026-04-01.
How severe is CVE-2026-34513?: High severity. CVSS v3 base score is 7.5 out of 10.