high CVSS 7.5

CVE-2026-34513·Python vulnerability

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.

Severity
high
Software
Python
Fixed in
3.13.4
Published
2026-04-01

Affected versions

Until: 3.13.4

Fixed in: 3.13.4

How to fix this CVE

Update AIOHTTP to version 3.13.4 or later to address an unbounded DNS cache vulnerability that can lead to excessive memory consumption. Organizations running AIOHTTP-dependent Python applications should prioritize this update to prevent potential denial-of-service conditions caused by uncontrolled cache growth. Verify the update by checking the installed package version and testing DNS resolution behavior under typical application load.

sudo dnf update python3-aiohttp

Defensia detects this vulnerability

How to check if you are affected

  1. Step 1: Check the installed AIOHTTP version by running: python3 -c "import aiohttp; print(aiohttp.__version__)"
  2. Step 2: Review application logs for memory usage spikes or out-of-memory errors, particularly in systems performing frequent DNS lookups
  3. Step 3: Monitor DNS resolver cache size using: cat /proc/net/stat/nf_conntrack | tail -1 to identify abnormal cache growth patterns
  4. Step 4: Verify the patch by re-running the version check and confirming version 3.13.4 or higher is installed

FAQ

What is CVE-2026-34513?

CVE-2026-34513 is a memory exhaustion vulnerability in AIOHTTP where the DNS cache fails to enforce size limits, allowing attackers to trigger unbounded cache growth that consumes system memory and potentially causes service disruption.

Is CVE-2026-34513 being actively exploited?

No, this vulnerability is not currently listed on the CISA KEV catalog and no public exploits are available, though organizations should still apply the fix promptly to reduce DoS risk.

What versions of Python are affected by CVE-2026-34513?

All versions of AIOHTTP prior to 3.13.4 are affected; the vulnerability affects AIOHTTP running on Python 3.x environments across all supported distributions.

How do I check if my server is vulnerable to CVE-2026-34513?

Run: python3 -c "import aiohttp; print(aiohttp.__version__)" and compare the output to version 3.13.4; versions below 3.13.4 are vulnerable.

Does Defensia detect CVE-2026-34513?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If AIOHTTP or Python is installed on a monitored server, CVE-2026-34513 will appear in your dashboard with remediation steps.

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References

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