jackson-core: Number length constraint bypass in non-blocking (async) JSON parser leads to potential denial of service

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-18401
StatePUBLISHED
AssignerHeroDevs
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-04 15:16:29 UTC
Updated2026-08-04 19:16:43 UTC
DescriptionThe non-blocking (asynchronous) JSON parser in jackson-core does not enforce the maxNumberLength constraint defined in StreamReadConstraints (default: 1000 characters). An attacker able to submit JSON to an application that uses the async parser API can supply a number token of arbitrary length, leading to excessive memory allocation and potential CPU exhaustion, resulting in a denial of service. The synchronous parser enforces this limit correctly, so the constraint is applied inconsistently depending on which parsing API the application uses. Root cause: the async parsing path in NonBlockingUtf8JsonParserBase and related classes never invokes the number length validation methods. Number parsing methods such as _finishNumberIntegralPart() accumulate digits into the TextBuffer without any length check, then call _valueComplete() to finalize the token. _valueComplete() does not call resetInt() or resetFloat(), which are the methods in ParserBase where validateIntegerLength() and validateFPLength() are performed. Because that validation step is skipped, maxNumberLength is never enforced on the async code path. Impact: an attacker sending a JSON document containing an arbitrarily long number to an application using the async parser (for example a Spring WebFlux or other reactive application) can cause unbounded allocation in the TextBuffer and an OutOfMemoryError. If the application subsequently calls getBigIntegerValue() or getDecimalValue(), the JVM may additionally be tied up in O(n^2) BigInteger parsing, causing CPU-based denial of service. No privileges or user interaction beyond the ability to submit data for parsing are required. This issue affects com.fasterxml.jackson.core:jackson-core from version 2.15.0 through 2.18.5 and from 2.19.0 through 2.21.0, and tools.jackson.core:jackson-core from 3.0.0 through 3.0.x. Versions prior to 2.15.0 are not affected, because StreamReadConstraints -- which defines the maxNumberLength setting -- was first introduced in jackson-core 2.15.0, so no such constraint exists to be bypassed in earlier releases. Note that GHSA-72hv-8253-57qq records the lower bound of the affected 2.x range as 2.0.0.

Risk And Classification

Primary CVSS: v4.0 6.9 MEDIUM from 36c7be3b-2937-45df-85ea-ca7133ea542c

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Problem Types: CWE-770 | CWE-770 CWE-770 Allocation of Resources Without Limits or Throttling

VersionSourceTypeScoreSeverityVector
4.036c7be3b-2937-45df-85ea-ca7133ea542cSecondary6.9MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/C...
4.0CNACVSS6.9MEDIUMCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

CVSS v4.0 Breakdown

Attack Vector
Network
Attack Complexity
Low
Attack Requirements
None
Privileges Required
None
User Interaction
None
Confidentiality
None
Integrity
None
Availability
Low
Sub Conf.
None
Sub Integrity
None
Sub Availability
None

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA FasterXML Jackson-core affected 2.15.0 2.18.5 maven Not specified
CNA FasterXML Jackson-core unaffected 2.18.6 maven Not specified
CNA FasterXML Jackson-core affected 2.19.0 2.21.1 maven Not specified
CNA FasterXML Jackson-core unaffected 2.21.1 maven Not specified
CNA FasterXML Jackson-core affected 3.0.0 3.1.0 maven Not specified
CNA FasterXML Jackson-core unaffected 3.1.0 maven Not specified

References

ReferenceSourceLinkTags
github.com/FasterXML/jackson-core/commit/b0c428e6f993e1b5ece5c1c3cb2523e... 36c7be3b-2937-45df-85ea-ca7133ea542c github.com
github.com/FasterXML/jackson-core/security/advisories/GHSA-72hv-8253-57qq 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
github.com/FasterXML/jackson-core/pull/1555 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: sprabhav7 (en)

CNA: rohan-repos (en)

CNA: neilmadden-hazelcast (en)

CNA: awsactran (en)

CNA: pjfanning (PJ Fanning) (en)

CNA: cowtowncoder (Tatu Saloranta) (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-02-22T20:17:00.000ZFix merged upstream via FasterXML/jackson-core#1555 (milestone 2.18.6)
CNA2026-02-26T00:00:00.000ZGHSA-72hv-8253-57qq published by the maintainer in FasterXML/jackson-core
CNA2026-02-28T00:00:00.000ZAdvisory reviewed and published to the GitHub Advisory Database

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