Bug 2538720 (CVE-2026-89407)

Summary: CVE-2026-89407 com.fasterxml.jackson/jackson-core: tools.jackson.core/jackson-core: Jackson-core: Denial of Service via regular expression backtracking
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: aakkiang, abrianik, alinfoot, amctagga, anthomas, ant, anujha, aoconnor, aschwart, asoldano, asyoung, aszczucz, ataylor, bbaranow, bbrownin, bmaxwell, bniver, boliveir, bstansbe, ccranfor, cescoffi, cfu, cmah, csuconic, csutherl, dbruscin, dfreiber, dhanak, dlofthou, drichtar, drosa, drow, dschmidt, dsimansk, dsoumis, dtrifiro, ebaron, edewata, eglynn, ehelms, ehugonne, ewittman, flucifre, fmariani, fmongiar, gbenhaim, ggainey, ggrzybek, gkimetto, gmalinko, gmeno, groman, gsmet, gtanzill, gtully, ikhan, istudens, ivassile, iweiss, janstey, jburrell, jbuscemi, jclere, jhollowa, jjoyce, jlanda, jmagne, jmartisk, jnethert, jpasqual, jpechane, jpretori, jraez, jschluet, jsherman, juwatts, jwon, kaycoth, kingland, kshier, kvanderr, lhh, manderse, mbenjamin, mburns, mcarlett, mdellweg, mfargett, mgarciac, mhackett, mhulan, mnovotny, mosmerov, mposolda, msvehla, nipatil, niyer, nmoumoul, nwallace, olubyans, osousa, ozzy, pantinor, parichar, pberan, pcreech, pdelbell, pesilva, pjindal, plodge, pmackay, prichard, prisingh, rbobbitt, rchan, rgemmell, rgodfrey, rguimara, rhel-process-autobot, rkubis, rmartinc, rmaucher, rstancel, rstepani, sausingh, sbiarozk, sdawley, simaishi, skhandel, smallamp, snegrini, sostapov, ssilvert, stcannon, sthirugn, sthorger, szappis, taherrin, tasato, tbish, tcunning, thjenkin, tlavocat, tmalecek, twaugh, varjain, vdosoudi, vereddy, vkumar, vmuzikar, watson-tool-maintainers, weaton, yfang, yguenane
Target Milestone: ---Keywords: Security
Target Release: ---   
Hardware: All   
OS: Linux   
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Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in jackson-core. An attacker can supply specially crafted JSON that, when deserialized into a numeric target type, triggers a Regular expression Denial of Service (ReDoS) vulnerability. This occurs due to quadratic backtracking in the NumberInput.looksLikeValidNumber() method's PATTERN_FLOAT regular expression. A small number of concurrent requests with a long input string can exhaust a server's request-handling thread pool, leading to a Denial of Service (DoS).
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:
Bug Depends On: 2542919, 2542920, 2542921, 2542923, 2542924, 2542927    
Bug Blocks:    

Description OSIDB Bzimport 2026-09-22 20:09:28 UTC 
NumberInput.looksLikeValidNumber() in FasterXML jackson-core pre-validates "stringified numbers" with two regular expressions: PATTERN_FLOAT ([+-]?[0-9]*[\.]?[0-9]+([eE][+-]?[0-9]+)?), present since 2.17.0, and PATTERN_FLOAT_TRAILING_DOT, added in 2.17.2. PATTERN_FLOAT places adjacent quantifiers over the same character class -- an optional [0-9]* run, an optional dot, then a required [0-9]+ run -- so input that ultimately fails to match forces Java's backtracking engine to retry every possible split point of the digit run. 



Matching cost therefore grows with the square of the input length. 



An attacker who can supply JSON that an application deserializes into a numeric target type reaches this method through jackson-databind's default String-to-number coercion (StdDeserializer and NumberDeserializers for BigDecimal, BigInteger, Double and Float). 



Because StreamReadConstraints.maxStringLength defaults to 20,000,000 characters, no constraint bounds the input before it reaches the regex. 



Testing by the reporter confirmed O(n^2) growth across five consecutive input-size doublings, with a single 160,000-character string consuming roughly 74 seconds in one call; a small number of concurrent requests of ordinary body size can therefore exhaust a server's request-handling thread pool. 



The affected method does not exist before 2.17.0, so 2.16.x and earlier releases are not affected. 



The fix replaces both regular expressions with a hand-rolled single-pass scan.