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VulnerabilityPublished

CVE-2026-8466: ninenines cowboy · Unthrottled Resource Allocation

Affects ninenines cowboySource CVE Database V5

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Not known to be exploited · CVSS 8.2 High : upgrade to 2.15.0 soon.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 4.0 base score
8.2High
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.3% chance of exploitation in 30 days – higher than 32% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 2.15.0, 5c6a2061b41bb5771c4659fac7d5a822dca5bafb
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 13 May 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 cowboy to 2.15.0; cowboy to 5c6a2061b41bb5771c4659fac7d5a822dca5bafb.

Affected software

ProductAffectedFixed in
nineninescowboyAffected
  • >=2.0.0 <2.15.0
Fixed in
  • 2.15.0
nineninescowboyAffected
  • ≥ 917cf99e10c41676183d501b86af6e47c95afb89, < 5c6a2061b41bb5771c4659fac7d5a822dca5bafb
Fixed in
  • 5c6a2061b41bb5771c4659fac7d5a822dca5bafb
GitHubninenines/cowboypkg:github/ninenines/cowboyOther threatsAffected
  • =2.0.0
Fixed in–
Hexcowboypkg:hex/cowboyOther threatsAffected
  • >=2.0.0 <2.15.0
Fixed in
  • 2.15.0

CPE configurations (1)

  • cpe:2.3:a:ninenines:cowboy:*:*:*:*:*:*:*:*

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

AI-suggested

If you cannot patch yet, consider implementing external request size limits or rate limiting multipart/form-data requests at a proxy or firewall level to mitigate potential exploitation.

Description

CVE-2026-8466 is a high-severity vulnerability in the ninenines cowboy HTTP server version 2.0.0. It allows an unauthenticated attacker to cause a denial of service by exploiting the lack of limits on resource allocation during multipart header parsing. The vulnerable function accumulates request bytes into a buffer without an upper bound, leading to memory exhaustion. This can be triggered by sending multipart/form-data requests that never complete the header section, potentially exhausting BEAM memory with only a few concurrent malicious uploads.

References

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