Bug 2511022 (CVE-2026-18401)

Summary:	CVE-2026-18401 tools.jackson.core/jackson-core: com.fasterxml.jackson.core/jackson-core: jackson-core: Denial of Service due to number length bypass in asynchronous JSON parser
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	unspecified	CC:	aakkiang, aazores, abrianik, alinfoot, anthomas, ant, anujha, aschwart, asoldano, asyoung, aszczucz, ataylor, avibelli, bbaranow, bbrownin, bgeorges, bmaxwell, boliveir, bstansbe, ccranfor, cescoffi, cfu, chfoley, cmah, csutherl, dandread, dbruscin, dfreiber, dhanak, dkreling, dlofthou, drichtar, drosa, drow, dschmidt, dsimansk, dsoumis, dtrifiro, eaguilar, ebaron, edewata, ehelms, ehugonne, ewittman, fmariani, fmongiar, ggainey, ggrzybek, gkimetto, gmalinko, gsmet, gtanzill, istudens, ivassile, iweiss, janstey, jburrell, jbuscemi, jclere, jhollowa, jlanda, jmagne, jmartisk, jmatsuok, jnethert, jpasqual, jpechane, jraez, jtolenti, juwatts, jwon, kaycoth, kgaikwad, kingland, kshier, kvanderr, lthon, manderse, mcarlett, mdellweg, mfargett, mhulan, mnovotny, mosmerov, mposolda, msvehla, nipatil, nmoumoul, nwallace, olubyans, osousa, pantinor, parichar, pberan, pcreech, pesilva, pgallagh, pjindal, plodge, pmackay, prichard, prisingh, probinso, rbryant, rchan, rgodfrey, rguimara, rhel-process-autobot, rkubis, rmartinc, rmaucher, rruss, rstancel, rstepani, rsvoboda, sausingh, sbiarozk, sdawley, simaishi, skhandel, smallamp, snegrini, ssilvert, stcannon, sthirugn, sthorger, swoodman, szappis, taherrin, tasato, tcunning, teagle, thjenkin, tmalecek, tqvarnst, vdosoudi, vkumar, vmuzikar, watson-tool-maintainers, weaton, yfang, yguenane
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in jackson-core. The non-blocking (asynchronous) JSON parser does not properly enforce the maximum number length constraint. A remote attacker can exploit this by submitting a specially crafted JSON document containing an arbitrarily long number to an application using the asynchronous parser. This can lead to excessive memory allocation and CPU exhaustion, resulting in a denial of service (DoS) for the affected application.	Story Points:	---
Clone Of:		Environment:
Last Closed:		Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:
Bug Depends On:	2513127, 2513128, 2513129, 2513130, 2513131, 2513132
Bug Blocks:

Description OSIDB Bzimport 2026-08-04 15:02:07 UTC

The 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.