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CVE-2026-91776— jackson-databind: unbounded growth of the type id cache in TypeDeserializerBase retains every unknown raw type ID

Quick assessment

Affected
FasterXML jackson-databind
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

TypeDeserializerBase._findDeserializer() in FasterXML jackson-databind caches the resolved deserializer under the raw, attacker-supplied type ID. When name-based polymorphism is configured with a fallback, for example @JsonTypeInfo(use = Id.NAME, defaultImpl =

CVSS 7.5 · High
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I. Basic Information for CVE-2026-91776

Vulnerability Information

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Vulnerability Title
jackson-databind: unbounded growth of the type id cache in TypeDeserializerBase retains every unknown raw type ID
Source: CVE Program / CVE List V5
Vulnerability Description
TypeDeserializerBase._findDeserializer() in FasterXML jackson-databind caches the resolved deserializer under the raw, attacker-supplied type ID. When name-based polymorphism is configured with a fallback, for example @JsonTypeInfo(use = Id.NAME, defaultImpl = ...), every distinct unrecognized type ID resolves to the same fallback deserializer but is retained as its own key in the _deserializers map. That map has no configurable bound and lives for the lifetime of the type deserializer, so an attacker who can repeatedly supply fresh unknown type IDs causes monotonic memory retention across requests. The reporter observed 10,000 retained entries from 10,000 distinct unknown IDs, against a single entry for a control that repeated one unknown ID the same number of times, isolating attacker-controlled key cardinality from request volume. Exploitation requires an application that enables name-based polymorphism with a defaultImpl or equivalent fallback, accepts attacker-influenced type IDs, and reuses a long-lived ObjectMapper across requests. The fix stops caching fallback resolutions for unrecognized IDs and bounds both the number of cached entries and the length of a cacheable type ID.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
未加控制的资源消耗(资源穷尽)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
FasterXML jackson-databind 2.0.0 ~ 2.18.10 -
FasterXML jackson-databind 3.0.0 ~ 3.1.6 -

II. Public POCs for CVE-2026-91776

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III. Intelligence Information for CVE-2026-91776

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Other References for CVE-2026-91776 (2)

Same Patch Batch · FasterXML · 2026-09-23 · 3 CVEs total

CVE-2026-89425 7.5 HIGH jackson-core: UTF8DataInputJsonParser._reportInvalidToken() does not honor maxErrorTokenLe
CVE-2026-91777 7.5 HIGH jackson-databind: quadratic forward-reference completion in Collection and Map deserialize

IV. Related Vulnerabilities

Same product: jackson-databind
Same vendor: FasterXML
Same weakness: CWE-400

V. Comments for CVE-2026-91776

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