How severe is CVE-2026-54274?

No CVSS score has been assigned to CVE-2026-54274 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-54274?

CVE-2026-54274 affects the following packages: aiohttp (PyPI). Ecosystems affected: PyPI.

How do I fix CVE-2026-54274?

Update aiohttp to 3.14.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-54274 is resolved across your whole dependency graph.

How do I detect CVE-2026-54274 in my PyPI dependencies?

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.

How do I mitigate CVE-2026-54274 if there is no patch (or I can't update yet)?

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 does O3 Security protect against CVE-2026-54274?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-54274 can be triaged on real exposure rather than presence alone.

Is CVE-2026-54274 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-54274 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-54274?

CVE-2026-54274 has an EPSS (Exploit Prediction Scoring System) score of 0.5%, placing it in the 43th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-54274?

CVE-2026-54274 is classified as CWE-770 (CWE-770). This weakness type describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation.

When was CVE-2026-54274 published, and has it been updated?

CVE-2026-54274 was published on June 22, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐍 PyPI

Not in CISA KEV

CVE-2026-54274 — aiohttp

Fix: aio-libs/aiohttp@14b6ee8

CVE-2026-54274 is a CWE-770 vulnerability in aiohttp. A fix is available for aiohttp — see the affected versions and patch details below.

AIOHTTP: Incomplete websocket frame payloads bypass memory limits

Also known asGHSA-xcgm-r5h9-7989PYSEC-2026-2108

Published

Jun 22, 2026

Updated

Aug 12, 2026

Affected

1 pkg

Patched

1 / 1

Exploits

None indexed

Exploitation data as of Sep 25, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

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-2026-54274.

EPSS Exploitation Probability

via FIRST.org ↗

0.5%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs43th percentile — riskier than 43% of all scored CVEsHighest risk

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

1 pkg affected

🐍aiohttp

Real-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

Summary

If an attacker sends large incomplete websocket frame payloads, it may be possible to bypass the usual size limits on memory use.

Impact

If a web application has WebSocket endpoints, it may be possible for an attacker to execute a DoS attack through excessive memory use.

Patch: https://github.com/aio-libs/aiohttp/commit/14b6ee851fb16ec199acb950de0c82d476799e7d

Affected Packages

1 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐍PyPI	`aiohttp`	all versions	3.14.1`pip install --upgrade 'aiohttp==3.14.1'`

Detection & mitigation playbook

Open-source dependency

Detect
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-2026-54274 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-2026-54274 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-54274. 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.

Red HatModerate

This vulnerability is rated Moderate because an unauthenticated remote attacker can trigger denial of service against an affected aiohttp HTTP server with WebSocket endpoints by sending large incomplete WebSocket frame payloads that bypass memory size limits. Exploitation requires aiohttp deployed as a network-facing…

Workaround published by Red Hat

Update the aiohttp package to version 3.14.1 or later. Until updated builds are available, reduce exposure by not exposing aiohttp-based HTTP servers with WebSocket endpoints directly to untrusted networks. A reverse proxy or load balancer in front of the service can help limit abusive WebSocket traffic. Installations that use aiohttp only as an HTTP client, or that do not expose WebSocket endpoints, are not affected by this flaw.

Source: Red Hat security advisory for CVE-2026-54274 (CC BY 4.0)

Frequently Asked Questions

### Summary If an attacker sends large incomplete websocket frame payloads, it may be possible to bypass the usual size limits on memory use. ### Impact If a web application has WebSocket endpoints, it may be possible for an attacker to execute a DoS attack through excessive memory use. ----- Patch: https://github.com/aio-libs/aiohttp/commit/14b6ee851fb16ec199acb950de0c82d476799e7d

O3 Security · Impact-Aware SCA

Is CVE-2026-54274 in your dependencies?

O3 Security finds CVE-2026-54274 across PyPI dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

Scan my dependencies How O3 SCA works