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CVE-2026-91777— jackson-databind: quadratic forward-reference completion in Collection and Map deserializers

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.

Forward-reference completion for @JsonIdentityInfo object IDs in FasterXML jackson-databind performs a linear scan of the pending-reference accumulator for every resolved ID. The affected paths are CollectionDeserializer.CollectionReferringAccumulator.resolveF

CVSS 7.5 · High
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I. Basic Information for CVE-2026-91777

Vulnerability Information

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Vulnerability Title
jackson-databind: quadratic forward-reference completion in Collection and Map deserializers
Source: CVE Program / CVE List V5
Vulnerability Description
Forward-reference completion for @JsonIdentityInfo object IDs in FasterXML jackson-databind performs a linear scan of the pending-reference accumulator for every resolved ID. The affected paths are CollectionDeserializer.CollectionReferringAccumulator.resolveForwardReference() and the equivalent implementation in MapDeserializer. When a document first creates N unresolved object-ID references in an identity-enabled collection or map and then defines those same IDs in reverse order, completion performs on the order of N * (N + 1) / 2 identity comparisons, so a shallow document whose size grows linearly causes quadratic CPU work during deserialization. The reporter instrumented equals() calls on the ID class and measured exactly 2,003,000 comparisons at N = 2,000, against zero comparisons in the pending-reference lookup path for an equally sized control in which every reference was already resolved. The input requires no deep nesting and no syntactically unusual JSON. Exploitation requires an application that deserializes attacker-influenced JSON into an identity-enabled collection or map. The fix replaces the repeated linear lookup with a keyed pending-reference structure.
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 2.5.0 ~ 2.18.10 -
FasterXML jackson-databind 3.0.0 ~ 3.1.6 -

II. Public POCs for CVE-2026-91777

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III. Intelligence Information for CVE-2026-91777

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Other References for CVE-2026-91777 (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-2026-91776 7.5 HIGH jackson-databind: unbounded growth of the type id cache in TypeDeserializerBase retains ev

IV. Related Vulnerabilities

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

V. Comments for CVE-2026-91777

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