CVSS 3.1
7.5 highCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:HCVE-2026-126366
msgpack-java JRuby decoder allocates from declared header counts with no cap: 5-byte message forces multi-GiB OOM
High (7.5) in msgpack msgpack-ruby.
On this page
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.
Severity
- CWEs
- CWE-770 Allocation of Resources Without Limits or Throttling
CWE-1325 Improperly Controlled Sequential Memory Allocation - Published
- Assigned by
- GitHub_M (CNA)
- NVD analysis
- Not in the NVD yet
- Record from
- the CVE List, synced
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Affected
Versions
From the CNA's record in the CVE List.
| Product | Affected |
|---|---|
| msgpack-ruby | < 1.8.7 |
Attack patterns (CAPEC)
- CAPEC-130 Excessive Allocation Likelihood: Medium · Severity: Medium
The attack patterns MITRE's CAPEC relates to this record's weaknesses, as MITRE names them. Credits. More on the page of CWE-770 (20).