CVE-2026-8466: ninenines cowboy · Unthrottled Resource Allocation
Affects ninenines cowboySource CVE Database V5
Not known to be exploited · CVSS 8.2 High : upgrade to 2.15.0 soon.
Data as of 30 Oct 2026, 11:52 UTC
- 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:NExploitation evidence
Disclosed: evidence found.
CVE published 13 May 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by 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
| Product | Affected | Fixed in |
|---|---|---|
| nineninescowboy | Affected
| Fixed in
|
| nineninescowboy | Affected
| Fixed in
|
GitHubninenines/cowboypkg:github/ninenines/cowboyOther threats | Affected
| Fixed in– |
Hexcowboypkg:hex/cowboyOther threats | Affected
| Fixed in
|
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.