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VulnerabilityPublished Updated

CVE-2026-34517: aio-libs aiohttp · Unthrottled Resource Allocation

Affects aio-libs aiohttpSource CVE Database V5

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Not known to be exploited · CVSS 2.7 Low : upgrade to 3.13.4 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score
2.7Low
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 34% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 3.13.4
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:U

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 2 Apr 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: 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 30 Oct 2026.

What to do

Upgrade aio-libs aiohttp to 3.13.4.

Affected software

ProductAffectedFixed in
aio-libsaiohttpAffected
  • <3.13.4
Fixed in
  • 3.13.4
PyPIaiohttppkg:pypi/aiohttpOther threatsAffected
  • <3.13.4
Fixed in
  • 3.13.4

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

AI-suggested

Upgrade aiohttp to version 3.13.4 or later, where this issue has been fixed. No additional mitigation is required once the patch is applied.

Description

### Summary For some multipart form fields, aiohttp read the entire field into memory before checking client_max_size. ### Impact If an application uses `Request.post()` an attacker can send a specially crafted multipart request to force significant temporary memory allocation even when the request is ultimately rejected. ----- Patch: https://github.com/aio-libs/aiohttp/commit/cbb774f38330563422ca0c413a71021d7b944145

References

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