What is CVE-2026-91777?

CVE-2026-91777 is jackson-databind: quadratic forward-reference completion in Collection and Map deserializers. The supplied enrichment data classifies it as Denial of Service mapped to CWE-400 Uncontrolled Resource Consumption.

Which versions are affected?

Affected product and version evidence is listed in the product table above. Current public advisories should be checked for exact version scope before patch targeting is finalized.

Is there active exploitation?

Active exploitation is not confirmed from current sources for CVE-2026-91777. If exploitation is not confirmed from current sources, teams should document that status and continue monitoring KEV, vendor, and telemetry updates.

No. CVE-2026-91777 is not listed in CISA KEV in the supplied enrichment data. KEV status should be monitored because it can change after initial disclosure or after exploitation becomes publicly confirmed.

Is there a public exploit?

1 public PoC repositories reported; 0 marked weaponized in current dataset. Public exploit or PoC availability should raise triage priority, especially for exposed or business-critical systems.

How can defenders detect it?

Start with web/proxy/WAF logs, application logs, network IDS/IPS where available. Look for vulnerability-class behavior, product errors, suspicious authentication events, exploit probes, and abnormal process activity based only on evidence that applies to the affected product.

How should teams prioritize it?

Prioritize CVE-2026-91777 using CVSS 7.5, EPSS 0%, KEV status, public PoC status, and asset exposure. Internet-facing, privileged, or business-critical deployments should be handled first.

Are workarounds available?

Workarounds are not confirmed from current sources. Fixed-version evidence is listed in the mitigation section above.

Which threat actors are linked publicly?

No public threat actor linkage is confirmed from current sources. Do not attribute exploitation to a threat actor unless the source evidence explicitly supports that linkage.

What should be done in the next 24 hours?

Identify exposed assets running affected vendor/product/version combinations. Prioritize based on EPSS, PoC availability, and external exposure. Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class. Open remediation tickets with affected assets, owners, evidence status, and detection coverage so decisions are traceable.

highDenial of Servicepublic exploit

CVE-2026-91777

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

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.

Published Sep 23, 2026Updated Sep 23, 2026Sources: NVD, FasterXML (CNA), GitHub

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the scoring sources call it.

Exploitation

Exploit code

public exploit, none observed

EPSS

Not scored

FIRST has not published a score

Affects

FasterXML

5 products listed

CVSS base

7.5

high

Remediation

The vendor's own words where we have them.

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.

First 24 hours

Ordered from the record's own fields — exposure first, because you cannot patch what you have not found.

Identify exposed assets running affected vendor/product/version combinations.
Prioritize based on EPSS, PoC availability, and external exposure.
Search available logs for exploit probes, errors, authentication anomalies, or suspicious child processes matching the vulnerability class.

Affected scope

Vendor, product and version as the advisories word them.

Vendor	Product	Versions	Status
FasterXML	jackson-databind	2.5.0 to <= 2.18.10	Vulnerable
FasterXML	jackson-databind	2.19.0 to <= 2.21.6	Vulnerable
FasterXML	jackson-databind	2.22.0 to <= 2.22.2	Vulnerable
FasterXML	jackson-databind	3.0.0 to <= 3.1.6	Vulnerable
FasterXML	jackson-databind	3.2.0 to <= 3.2.2	Vulnerable

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Availability

High

Confidentiality

None

Integrity

None

Scope

Unchanged

Attack Complexity

Low

Attack Vector

Network

Privileges Req

None

User Interaction

None

Every base score collected

Sources score independently and disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Source
7.5	CVSS 3.1	high	3.9	3.6	CNA, FasterXML (CNA)

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Weakness & attack patterns

CWE-400Uncontrolled Resource Consumption

Inferred from the weakness class — not observed against this CVE.

CAPEC-125 · FloodingCAPEC-130 · Excessive Allocation

T1499Endpoint Denial of Service

Public exploit

Capability, not use: code existing is a different claim from anyone running it.

Repositories

Detection

Read off the CVSS vector and the weakness class. Starting points, not rules we have tested.

Prioritize edge telemetry for network-reachable jackson-databind.
Monitor for scanner or exploit-pattern traffic after 1 public PoC repositories were reported.

web/proxy/WAF logsapplication logsnetwork IDS/IPS

Timeline

What happened to this CVE, newest first — with the readings a source repeats on a schedule counted underneath rather than listed.

2026
Added · CVSS 3.1 7.5 (AV:N)
Sep 23, 2026 · NVD
Initial · CVE published
Sep 23, 2026 · NVD

References

2 on the record

github.com/FasterXML/jackson-databind/issues/6204
Exploit, Third Party Advisory
github.com/FasterXML/jackson-databind/security/advisories/GHSA-cxp5-3px4-pw24
Exploit, Third Party Advisory

Elsewhere on this site

FasterXMLevery CVE for this vendor
Denial of Servicesame class
CWE-400other pages naming this weakness

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record1

What should defenders know first?

CVE-2026-91777 is jackson-databind: quadratic forward-reference completion in Collection and Map deserializers, a high vulnerability affecting jackson-databind from FasterXML. The current evidence does not list it in CISA KEV, and the exploit status is: Active exploitation is not confirmed from current sources for CVE-2026-91777. Public exploit evidence is: 1 public PoC repositories reported; 0 marked weaponized in current dataset. The affected-version evidence is listed in the key facts and affected products tables. Defenders should first verify whether exposed or business-critical assets run those versions, then apply vendor patches or mitigations, restrict reachable attack surface, and preserve logs for detection review. CVSS 7.5 describes technical severity, while EPSS 0% helps estimate near-term exploit likelihood; neither replaces asset context. Unknown fields should remain explicit in tickets, and threat actor, IOC, victimology, or payload claims should not be added unless a cited source supports them. Monitor CISA KEV, vendor advisories, NVD changes, public PoC repositories, and internal telemetry for update triggers.