CVE-2026-126366
msgpack-java JRuby decoder allocates from declared header counts with no cap: 5-byte message forces multi-GiB OOM
MessagePack for Ruby is an implementation of the MessagePack binary serialization format. Prior to 1.8.7, the Java-platform msgpack gem for JRuby allocated arrays and byte buffers directly from attacker-controlled array32, str32, and bin32 declared sizes before confirming that corresponding elements or bytes were available. A short MessagePack header could therefore trigger a very large allocation or sustained heap growth when an application decoded untrusted input through MessagePack.unpack or MessagePack::Unpacker, potentially exhausting the shared JVM heap. map32 and declared counts at or above 2^31 did not use the affected allocation behavior. This issue is fixed in version 1.8.7.
Fixes and workarounds
Fix
msgpack (RubyGems): OSV reports a fixed version 1.8.7. Check the advisory for supported release branches.
Source: OSV GHSA-73v3-wf97-vpgjAffected products and versions
| Product | Versions | Authority |
|---|---|---|
| msgpack-ruby msgpack |
< 1.8.7 (affected) | CNA: GitHub_M |
msgpackmsgpack
RubyGems |
0.0.1 (affected, RubyGems) 0.2.0 (affected, RubyGems) 0.2.1 (affected, RubyGems) 0.2.2 (affected, RubyGems) 0.3.0 (affected, RubyGems) 0.3.1 (affected, RubyGems) 0.3.2 (affected, RubyGems) 0.3.3 (affected, RubyGems) 0.3.4 (affected, RubyGems) 0.3.5 (affected, RubyGems) 0.3.6 (affected, RubyGems) 0.3.7 (affected, RubyGems) 0.3.8 (affected, RubyGems) 0.3.9 (affected, RubyGems) 0.4.0 (affected, RubyGems) 0.4.1 (affected, RubyGems) 0.4.2 (affected, RubyGems) 0.4.3 (affected, RubyGems) 0.4.4 (affected, RubyGems) 0.4.5 (affected, RubyGems) 0.4.6 (affected, RubyGems) 0.4.7 (affected, RubyGems) 0.5.0 (affected, RubyGems) 0.5.1 (affected, RubyGems) 0.5.10 (affected, RubyGems) 0.5.11 (affected, RubyGems) 0.5.12 (affected, RubyGems) 0.5.2 (affected, RubyGems) 0.5.3 (affected, RubyGems) 0.5.4 (affected, RubyGems) 0.5.5 (affected, RubyGems) 0.5.6 (affected, RubyGems) 0.5.7 (affected, RubyGems) 0.5.8 (affected, RubyGems) 0.5.9 (affected, RubyGems) 0.6.0 (affected, RubyGems) 0.6.0pre1 (affected, RubyGems) 0.6.1 (affected, RubyGems) 0.6.2 (affected, RubyGems) 0.7.0 (affected, RubyGems) 0.7.0dev1 (affected, RubyGems) 0.7.1 (affected, RubyGems) 0.7.2 (affected, RubyGems) 0.7.2dev1 (affected, RubyGems) 0.7.3 (affected, RubyGems) 0.7.4 (affected, RubyGems) 0.7.5 (affected, RubyGems) 0.7.6 (affected, RubyGems) 1.0.0 (affected, RubyGems) 1.0.1 (affected, RubyGems) 1.0.2 (affected, RubyGems) 1.0.3 (affected, RubyGems) 1.1.0 (affected, RubyGems) 1.2.0 (affected, RubyGems) 1.2.1 (affected, RubyGems) 1.2.10 (affected, RubyGems) 1.2.2 (affected, RubyGems) 1.2.3 (affected, RubyGems) 1.2.4 (affected, RubyGems) 1.2.5 (affected, RubyGems) 1.2.6 (affected, RubyGems) 1.2.7 (affected, RubyGems) 1.2.8 (affected, RubyGems) 1.2.9 (affected, RubyGems) 1.3.0 (affected, RubyGems) 1.3.1 (affected, RubyGems) 1.3.2 (affected, RubyGems) 1.3.3 (affected, RubyGems) 1.4.0 (affected, RubyGems) 1.4.0.pre1 (affected, RubyGems) 1.4.1 (affected, RubyGems) 1.4.2 (affected, RubyGems) 1.4.3 (affected, RubyGems) 1.4.4 (affected, RubyGems) 1.4.4.pre1 (affected, RubyGems) 1.4.5 (affected, RubyGems) 1.5.0 (affected, RubyGems) 1.5.1 (affected, RubyGems) 1.5.2 (affected, RubyGems) 1.5.3 (affected, RubyGems) 1.5.4 (affected, RubyGems) 1.5.5 (affected, RubyGems) 1.5.6 (affected, RubyGems) 1.6.0 (affected, RubyGems) 1.6.1 (affected, RubyGems) 1.7.0 (affected, RubyGems) 1.7.1 (affected, RubyGems) 1.7.2 (affected, RubyGems) 1.7.3 (affected, RubyGems) 1.7.4 (affected, RubyGems) 1.7.5 (affected, RubyGems) 1.8.0 (affected, RubyGems) 1.8.1 (affected, RubyGems) 1.8.2 (affected, RubyGems) 1.8.3 (affected, RubyGems) 1.8.4 (affected, RubyGems) 1.8.5 (affected, RubyGems) 1.8.6 (affected, RubyGems) Ecosystem version events: introduced 0; fixed 1.8.7 Source events (ECOSYSTEM)Other versions: unaffected |
OSV GHSA-73v3-wf97-vpgj |
Version ranges are source assertions. Check the vendor advisory and your installed configuration before determining exposure.
CVSS assessments
| Version / score | Vector | Authority |
|---|---|---|
| 3.1 / 7.5 high |
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H | CNA: GitHub_M |
Exploit evidence
No exploit evidence in collected sources. This is not proof of no exploitation.
References
- https://github.com/msgpack/msgpack-ruby/security/advisories/GHSA-73v3-wf97-vpgjCNA: GitHub_M · x_refsource_CONFIRM
- https://github.com/msgpack/msgpack-ruby/commit/ca0efc1256c687b428c46dd68ce000ff515d53f2CNA: GitHub_M · x_refsource_MISC
- https://github.com/msgpack/msgpack-ruby/releases/tag/v1.8.6CNA: GitHub_M · x_refsource_MISC
- https://github.com/msgpack/msgpack-ruby/releases/tag/v1.8.7CNA: GitHub_M · x_refsource_MISC
- https://github.com/advisories/GHSA-73v3-wf97-vpgjOSV / GitHub Security Advisories · advisory
- https://osv.dev/vulnerability/GHSA-73v3-wf97-vpgjOSV / GitHub Security Advisories · osv
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