What is CVE-2026-54278?

CVE-2026-54278 is a high-severity vulnerability in Aiohttp, classified under Improper Handling of Highly Compressed Data (Data Amplification). CVSS score: 7.5/10. Published 2026-06-22.

How severe is CVE-2026-54278?

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

Vulnerability in Aiohttp

CVE-2026-54278

AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.1, during cleanup it is possible for a compressed request body to be decompressed into memory in one chunk. An attacker may be able to send a compressed payload in specific situations that could be decompressed into memory, potentially leading to DoS (a zip bomb edge case). This vulnerability is fixed in 3.14.1.

Published 2026-06-22 · last modified 2026-06-26.

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: 0.005 (40.0th percentile), scored 2026-09-30.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 40th percentile — 40.0% 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: 0.005 · change: +0.001

Affected products

Aiohttp
Aio-Libs Aiohttp — versions < 3.14.1

Weakness classification (CWE)

CWE-409 — Improper Handling of Highly Compressed Data (Data Amplification)

References

github.com/aio-libs/aiohttp/security/advisories/GHSA-g3cq-j2xw-wf74 (Third Party Advisory)
github.com/aio-libs/aiohttp/commit/4f7480e474cccc6a8cc2c92ad3f17a31dedf8232 (Patch)

Frequently asked questions

What is CVE-2026-54278?: CVE-2026-54278 is a high-severity vulnerability in Aiohttp, classified under Improper Handling of Highly Compressed Data (Data Amplification). CVSS score: 7.5/10. Published 2026-06-22.
How severe is CVE-2026-54278?: High severity. CVSS v3 base score is 7.5 out of 10.