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VulnerabilityPublished

CVE-2025-69227: aio-libs aiohttp · Infinite Loop

Affects aio-libs aiohttpSource CVE Database V5

0

Not known to be exploited · CVSS 6.6 Medium : upgrade to 3.13.3 when convenient.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 4.0 base score
6.6Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 33% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.13.3
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:U

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 5 Jan 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Upgrade aio-libs aiohttp to 3.13.3.

Affected software

ProductAffectedFixed in
aio-libsaiohttpAffected
  • <3.13.3
Fixed in
  • 3.13.3
PyPIaiohttppkg:pypi/aiohttpOther threatsAffected
  • <3.13.3
Fixed in
  • 3.13.3

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

  1. Upgrade all aiohttp dependencies to version 3.13.3 or later immediately to ensure the vulnerability is patched.
  2. Review Python runtime configurations and avoid running production environments with the -O or PYTHONOPTIMIZE=1 flags enabled, as these disable assert statements and trigger the vulnerability.
  3. Audit application code to identify usage of Request.post() handlers and validate input handling logic to ensure no reliance on assert statements for critical control flow.
  4. Implement rate limiting and anomaly detection on POST endpoints to mitigate potential DoS attempts.
  5. Use application-layer firewalls or WAFs to detect and block suspicious POST request patterns targeting aiohttp services.
  6. Monitor aiohttp server logs for unusual request patterns or performance degradation indicative of infinite loop conditions.
  7. Incorporate this vulnerability into vulnerability management and patching cycles, ensuring dependencies are regularly updated.
  8. Educate development teams on the risks of using assert statements for production input validation and encourage defensive programming practices.

Description

CVE-2025-69227 is a medium severity vulnerability in aiohttp versions prior to 3.13.3 that can cause an infinite loop leading to a denial-of-service (DoS) attack. The flaw arises when Python optimizations are enabled (using -O or PYTHONOPTIMIZE=1), which bypass assert statements in aiohttp's handling of POST requests. An attacker can send a specially crafted POST request to trigger this infinite loop, causing the server to hang and become unresponsive. No authentication or user interaction is required, and the attack can be executed remotely over the network. This vulnerability affects asynchronous Python applications using aiohttp for HTTP client/server functionality. The issue is fixed in aiohttp version 3.13.3.

References

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