Attacker-controlled object instantiation via Comparable validator omission
Published Sep 1, 2026 · Updated Sep 1, 2026
Deserialization of untrusted data in FasterXML jackson-databind allows remote attackers to instantiate attacker-chosen Comparable types. DefaultBaseTypeLimitingValidator omits java.lang.Comparable from its unsafe-base-type set and unconditionally approves subtypes of every base type outside that set. Exploitation requires an @JsonTypeInfo-annotated Comparable base with no restrictive custom validator; the demonstrated result is construction of a java.io.File for an attacker-chosen path, not code execution by deserialization alone.
Summary
What happened
Deserialization of untrusted data in FasterXML jackson-databind allows remote attackers to instantiate attacker-chosen Comparable types. DefaultBaseTypeLimitingValidator omits java.lang.Comparable from its unsafe-base-type set and unconditionally approves subtypes of every base type outside that set. Exploitation requires an @JsonTypeInfo-annotated Comparable base with no restrictive custom validator; the demonstrated result is construction of a java.io.File for an attacker-chosen path, not code execution by deserialization alone.
The record
- CVE
- CVE-2026-83557
- Published
- Sep 1, 2026
- Updated
- Sep 1, 2026
- Vendor
- FasterXML
- Product
- jackson-databind
- Classifications
- CWE-502
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Sep 1, 2026CVE publishedPublication date reported by the CVE source.
- Sep 1, 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=2.11.0 <2.18.10
- Affected versionversion=2.19.0 <2.21.6
- Affected versionversion=2.22.0 <2.22.2
- Affected versionversion=3.0.0 <3.1.6
- Affected versionversion=3.2.0 <3.2.2
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- GHSA-gx83-3vf8-gh7j Comparable subtype proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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