CVE-2026-126366: msgpack-ruby · Unthrottled Resource Allocation
Affects msgpack-rubySource CVE Database V5
Not known to be exploited · CVSS 7.5 High : upgrade to 1.8.7 soon.
Data as of 12 Nov 2026, 22:51 UTC
Thin evidence
One scorer or none| CNA (GitHub_M) | CVSS 3.1 | 7.5 |
|---|
- Patch
- Available – fixed in 1.8.7
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HExploitation evidence
Disclosed: evidence found.
CVE published 12 Nov 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 12 Nov 2026.
What to do
Upgrade msgpack-ruby to 1.8.7.
Affected software
| Product | Affected | Fixed in |
|---|---|---|
| msgpackmsgpack-ruby | Affected
| Fixed in
|
AI-suggested
Upgrade msgpack-ruby to version 1.8.7 or later, where this allocation issue is fixed. No other mitigation is required as the fix addresses the root cause.
Description
CVE-2026-126366 is a vulnerability in msgpack-ruby prior to version 1.8.7 where the library allocates arrays and byte buffers based on attacker-controlled sizes without verifying the actual data length. This can lead to excessive memory allocation or sustained heap growth when decoding untrusted input, potentially exhausting the JVM heap. The issue is fixed in version 1.8.7.
References
- github.com/msgpack/msgpack-ruby/security/advisories/GHSA-73v3-wf97-vpgj (opens in a new tab)
- github.com/msgpack/msgpack-ruby/commit/ca0efc1256c687b428c46dd68ce000ff515d53f2 (opens in a new tab)
- github.com/msgpack/msgpack-ruby/releases/tag/v1.8.6 (opens in a new tab)
- github.com/msgpack/msgpack-ruby/releases/tag/v1.8.7 (opens in a new tab)