jackson-databind: quadratic forward-reference completion in Collection and Map deserializers
Summary
| CVE | CVE-2026-91777 |
|---|---|
| State | PUBLISHED |
| Assigner | HeroDevs |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-23 03:17:04 UTC |
| Updated | 2026-09-23 03:17:04 UTC |
| 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. |
Risk And Classification
Primary CVSS: v3.1 7.5 HIGH from 36c7be3b-2937-45df-85ea-ca7133ea542c
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Problem Types: CWE-400 | CWE-400 CWE-400 Uncontrolled Resource Consumption
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 3.1 | 36c7be3b-2937-45df-85ea-ca7133ea542c | Secondary | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
| 3.1 | CNA | CVSS | 7.5 | HIGH | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H |
CVSS v3.1 Breakdown
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | FasterXML | Jackson-databind | affected 2.5.0 2.18.10 maven | Not specified |
| CNA | FasterXML | Jackson-databind | affected 2.19.0 2.21.6 maven | Not specified |
| CNA | FasterXML | Jackson-databind | affected 2.22.0 2.22.2 maven | Not specified |
| CNA | FasterXML | Jackson-databind | affected 3.0.0 3.1.6 maven | Not specified |
| CNA | FasterXML | Jackson-databind | affected 3.2.0 3.2.2 maven | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/FasterXML/jackson-databind/security/advisories/GHSA-cxp5-3px4... | 36c7be3b-2937-45df-85ea-ca7133ea542c | github.com | |
| github.com/FasterXML/jackson-databind/issues/6204 | 36c7be3b-2937-45df-85ea-ca7133ea542c | github.com | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Daniel Birtwhistle (dabirt) (en)
Additional Advisory Data
Solutions
CNA: Upgrade to com.fasterxml.jackson.core:jackson-databind 2.18.11, 2.21.7 or 2.22.3, or to tools.jackson.core:jackson-databind 3.1.7 or 3.2.3. Lines 2.5.x through 2.17.x, 2.19.x, 2.20.x and 3.0.x received no fix on their own branch and are no longer maintained upstream.
Workarounds
CNA: Bound the size of JSON documents deserialized into @JsonIdentityInfo-enabled collections and maps, and cap the number of elements accepted for such types, so that the quadratic term cannot be driven large. Removing @JsonIdentityInfo from types reachable from attacker-influenced input avoids the code path entirely. Wall-clock timeouts on deserialization limit the impact of a single request.