CVE-2026-54273 — aiohttp
Fix: aio-libs/aiohttp@dfdfa9dCVE-2026-54273 is a CWE-770 vulnerability in aiohttp. A fix is available for aiohttp — see the affected versions and patch details below.
AIOHTTP: HTTP/1 Pipelined Requests Queue Without Limit
Exploitation Status
No confirmed exploitation observed yet
- CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.
- CISA’s own triage has not observed active exploitation or public proof-of-concept code for this CVE as of its last assessment.
Exploitation and automatability from CISA’s SSVC triage for CVE-2026-54273.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Real-World Exposure
aiohttpReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
AIOHTTP is an asynchronous HTTP client/server framework for asyncio and Python. Prior to 3.14.1, no limit was present on the number of pipelined requests that could be queued. An attacker may be able to use pipelined requests to use excessive amounts of memory, potentially leading to DoS. This vulnerability is fixed in 3.14.1.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | aiohttp | all versions | 3.14.1pip install --upgrade 'aiohttp==3.14.1' |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for aiohttp, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update aiohttp to 3.14.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54273 is resolved across your whole dependency graph.
Workarounds
Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-54273 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2026-54273. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Fixing This On Your OS
If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.
This vulnerability is rated Moderate because an unauthenticated remote attacker can trigger denial of service against an affected aiohttp HTTP/1 server by sending a large number of pipelined requests, causing excessive memory consumption. Exploitation requires aiohttp to be deployed as an HTTP/1 server that accepts…
Update the aiohttp package to version 3.14.1 or later. Until updated builds are available for a given product, reduce exposure by not exposing aiohttp-based HTTP/1 servers directly to untrusted networks. A reverse proxy in front of the service can help limit abusive pipelined request patterns. Installations that use aiohttp only as an HTTP client, or that do not accept HTTP/1 pipelined requests on an aiohttp server, are not affected by this flaw.Source: Red Hat security advisory for CVE-2026-54273 (CC BY 4.0)
Frequently Asked Questions
Is CVE-2026-54273 in your dependencies?
O3 Security finds CVE-2026-54273 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.