high CVSS 7.5 EPSS 0.28%

CVE-2026-54273·Python vulnerability

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.

Severity
high
Software
Python
Fixed in
3.14.1
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.28% — higher than 20% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2026-54273 scores 7.5 on CVSS, so a successful attack would be serious — but at 0.28%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

Until: 3.14.1

Fixed in: 3.14.1

How to fix this CVE

Update AIOHTTP to version 3.14.1 or later to mitigate a memory exhaustion denial-of-service vulnerability triggered by unbounded pipelined HTTP requests. Organizations running Python applications with vulnerable AIOHTTP versions should prioritize this update to prevent attackers from causing service degradation through memory consumption attacks.

sudo dnf update python3-aiohttp && sudo systemctl restart <your-python-service>

Defensia detects this vulnerability

WAF mitigation (if patching is not yet possible)

Add this rule to your WAF to block exploitation attempts while you schedule the patch. 

Implement request rate limiting and connection throttling on reverse proxies (Nginx, Apache) to restrict the number of pipelined requests per client: limit_requests_per_connection = 10 in Nginx or RequestLimitPerConnection in Apache. Additionally, configure read timeouts and total connection limits to prevent resource exhaustion.

How to check if you are affected

  1. Check installed AIOHTTP version: python3 -c "import aiohttp; print(aiohttp.__version__)"
  2. Identify AIOHTTP usage in your Python applications: grep -r "import aiohttp" /opt /srv /home --include="*.py" 2>/dev/null
  3. Monitor system memory usage during operation: while true; do free -h | grep Mem; sleep 5; done and correlate with incoming HTTP request patterns
  4. Verify the patch: python3 -c "import aiohttp; print('3.14.1' <= aiohttp.__version__)" should return True after remediation

FAQ

What is CVE-2026-54273?

CVE-2026-54273 is a memory exhaustion vulnerability in AIOHTTP that allows remote attackers to queue unlimited pipelined HTTP requests without enforcement, causing excessive memory consumption and potential service denial.

Is CVE-2026-54273 being actively exploited?

No, this vulnerability is not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog and no public exploits are available, though the attack method is straightforward and organizations should not delay patching.

What versions of Python are affected by CVE-2026-54273?

The vulnerability affects AIOHTTP versions prior to 3.14.1; all Python versions running affected AIOHTTP releases are impacted regardless of Python version itself.

How do I check if my server is vulnerable to CVE-2026-54273?

Run 'python3 -m pip list | grep aiohttp' or 'python3 -c "import aiohttp; print(aiohttp.__version__)"' to identify the installed version; if it is below 3.14.1, your deployment is vulnerable.

Does Defensia detect CVE-2026-54273?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Python and AIOHTTP are installed on a monitored server, CVE-2026-54273 will appear in your dashboard with remediation steps.

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References

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