Data substitution via overflowing MAP32 element count
Published Sep 12, 2026 · Updated Sep 12, 2026
Integer overflow in MessageUnpacker.skipValue() in MessagePack for Java 0.9.12 and earlier allows attackers to substitute later parsed fields. For MAP32 containers, the method doubles the untrusted 32-bit element count in a signed int without an overflow check, so counts at or above 0x40000000 wrap and terminate skipping early. An application must pass attacker-controlled MessagePack data to skipValue(); the resulting cursor desynchronization returns attacker-controlled data where subsequent fields are expected.
Summary
What happened
Integer overflow in MessageUnpacker.skipValue() in MessagePack for Java 0.9.12 and earlier allows attackers to substitute later parsed fields. For MAP32 containers, the method doubles the untrusted 32-bit element count in a signed int without an overflow check, so counts at or above 0x40000000 wrap and terminate skipping early. An application must pass attacker-controlled MessagePack data to skipValue(); the resulting cursor desynchronization returns attacker-controlled data where subsequent fields are expected.
The record
- CVE
- CVE-2026-90473
- Published
- Sep 12, 2026
- Updated
- Sep 12, 2026
- Vendor
- MessagePack
- Product
- MessagePack for Java
- Classifications
- Unavailable
- Attack vector
- Unavailable
- Privileges
- Unavailable
Timeline
How it unfolded
- Sep 12, 2026CVE publishedPublication date reported by the CVE source.
- Sep 12, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=0 <=0.9.12
What conditions does exploitation require?
What is affected?
Published CVSS scores
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Attacks
What attackers are doing with it
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Weakness, pattern, technique
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Public exploit references
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Technologies
Your stack
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Your stack
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