jackson-core: Async parser maxNumberLength bypass via chunked digit accumulation (incomplete fix for CVE-2026-18401 / GHSA-72hv-8253-57qq)

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2026-68494
StatePUBLISHED
AssignerHeroDevs
Source PriorityCVE Program / NVD first with legacy fallback
Published2026-08-04 15:16:41 UTC
Updated2026-08-04 19:16:52 UTC
DescriptionThe fix released in jackson-core 2.18.6 and 2.21.1 for CVE-2026-18401 (GHSA-72hv-8253-57qq, number length constraint bypass in the non-blocking parser) is incomplete. This record covers the remaining bypass. The earlier fix wired validateIntegerLength() into a new _setIntLength() helper and invoked it wherever the integer portion of a number is decided: a terminator byte arrives, a . or e/E is seen, or input ends inside a fully buffered value. It was not invoked on the attacker-relevant path where the parser runs out of input while still inside the MINOR_NUMBER_INTEGER_DIGITS minor state and returns NOT_AVAILABLE to the caller. As a result, an attacker who streams JSON to a non-blocking parser in many small chunks, without ever sending a terminator byte, keeps the parser inside MINOR_NUMBER_INTEGER_DIGITS indefinitely. _textBuffer.expandCurrentSegment() grows the accumulator on every chunk while validateIntegerLength() is never called. The accumulator is bounded only by maxStringLength (20 MiB by default) rather than by maxNumberLength (1000 by default), an amplification of roughly 20,000x over the documented limit. Because Java char values occupy two bytes, a single connection can be driven to approximately 40 MiB of heap before the validator finally fires when the value completes. The equivalent fraction-path code is correct: _finishFloatFraction() calls _setFractLength() before its NOT_AVAILABLE return. The missing call affects the integer-digit paths in _startPositiveNumber(), _startNegativeNumber() and _finishNumberIntegralPart() in NonBlockingUtf8JsonParserBase. Impact: reactive frameworks such as Spring WebFlux/Reactor, Quarkus, Helidon and Vert.x feed inbound HTTP or gRPC bytes to the async parser as they arrive, which is precisely the chunked-feed shape required. Operators who set StreamReadConstraints.maxNumberLength expecting it to cap memory per number value do not get that guarantee; memory accumulates per concurrent connection and attacker-controlled concurrency can exhaust the JVM heap. The synchronous parsers (UTF8StreamJsonParser, ReaderBasedJsonParser) and the async parser operating on complete input are not affected. Exploitation requires only the ability to stream data to a parsing endpoint; no privileges or user interaction are needed. This issue affects com.fasterxml.jackson.core:jackson-core from version 2.15.0 through 2.18.7, from 2.19.0 through 2.21.3, and from 2.22.0 through 2.22.0, and tools.jackson.core:jackson-core from 3.0.0 through 3.1.3 and from 3.2.0 through 3.2.0. 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-r7wm-3cxj-wff9 states the affected 2.x range without a lower bound.

Risk And Classification

Primary CVSS: v4.0 8.7 HIGH from 36c7be3b-2937-45df-85ea-ca7133ea542c

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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-ca7133ea542cSecondary8.7HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/C...
4.0CNACVSS8.7HIGHCVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/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
High
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:H/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 2.18.8 maven Not specified
CNA FasterXML Jackson-core unaffected 2.18.8 maven Not specified
CNA FasterXML Jackson-core affected 2.19.0 2.21.4 maven Not specified
CNA FasterXML Jackson-core unaffected 2.21.4 maven Not specified
CNA FasterXML Jackson-core affected 2.22.0 2.22.1 maven Not specified
CNA FasterXML Jackson-core unaffected 2.22.1 maven Not specified
CNA FasterXML Jackson-core affected 3.0.0 3.1.4 maven Not specified
CNA FasterXML Jackson-core unaffected 3.1.4 maven Not specified
CNA FasterXML Jackson-core affected 3.2.0 3.2.1 maven Not specified
CNA FasterXML Jackson-core unaffected 3.2.1 maven Not specified

References

ReferenceSourceLinkTags
github.com/FasterXML/jackson-core/commit/050b429804dce2a7e08f0be1b0b4c3d... 36c7be3b-2937-45df-85ea-ca7133ea542c github.com
github.com/FasterXML/jackson-core/pull/1611 36c7be3b-2937-45df-85ea-ca7133ea542c github.com
github.com/FasterXML/jackson-core/commit/4cdd529749da396cc7edf6d4a2aad41... 36c7be3b-2937-45df-85ea-ca7133ea542c github.com
github.com/FasterXML/jackson-core/security/advisories/GHSA-r7wm-3cxj-wff9 134c704f-9b21-4f2e-91b3-4a467353bcc0 github.com
www.cve.org/CVERecord 36c7be3b-2937-45df-85ea-ca7133ea542c www.cve.org
github.com/advisories/GHSA-72hv-8253-57qq 36c7be3b-2937-45df-85ea-ca7133ea542c github.com
github.com/FasterXML/jackson-core/commit/c5941e5aae7fd5aeac55d66933cfb82... 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: tonghuaroot (en)

CNA: tonghuaroot (en)

CNA: cowtowncoder (Tatu Saloranta) (en)

Additional Advisory Data

SourceTimeEvent
CNA2026-05-20T22:33:00.000ZFix merged upstream via FasterXML/jackson-core#1611 (milestone 2.18.8)
CNA2026-07-10T00:00:00.000ZGHSA-r7wm-3cxj-wff9 published by the maintainer in FasterXML/jackson-core
CNA2026-07-21T00:00:00.000ZAdvisory reviewed and published to the GitHub Advisory Database

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