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VulnerabilityPublished Updated

CVE-2026-34516: aio-libs aiohttp · Unthrottled Resource Allocation

Affects aio-libs aiohttpSource CVE Database V5

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Not known to be exploited · CVSS 6.6 Medium : upgrade to 3.13.4 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score
6.6Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.4% chance of exploitation in 30 days – higher than 39% 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:H/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 vulnerability has been patched. No other mitigation steps are indicated or necessary.

Description

### Summary A response with an excessive number of multipart headers may be allowed to use more memory than intended, potentially allowing a DoS vulnerability. ### Impact Multipart headers were not subject to the same size restrictions in place for normal headers, potentially allowing substantially more data to be loaded into memory than intended. However, other restrictions in place limit the impact of this vulnerability. ----- Patch: https://github.com/aio-libs/aiohttp/commit/8a74257b3804c9aac0bf644af93070f68f6c5a6f

References

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