CVE-2026-90473: msgpack-java through 0.9.12 Integer Overflow via MAP32

Vulnerability summary

CVE-2026-90473 is a medium (CVSS 6.9) Integer Overflow or Wraparound vulnerability in msgpack msgpack-java. EPSS estimates a 0.41% chance of exploitation in the next 30 days, higher than 35.4% of scored vulnerabilities.

Timeline

1. 12-09-2026
   PublishedVulnerability first disclosed.
2. 24-09-2026
   Last modifiedVulnerability information updated.

Description

msgpack-java through 0.9.12 contains an integer overflow vulnerability in MessageUnpacker.skipValue() when processing MAP32 containers with large element counts. Attackers can supply a MAP32 element count at or above 0x40000000 that wraps when doubled, causing the parser cursor to desynchronize and attacker-controlled data to be returned in place of later fields.

• CWE-190Integer Overflow or WraparoundThe product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.