Bug 2542703 (CVE-2026-102265)

Summary: CVE-2026-102265 pyjwt: pyjwt: Denial of Service via deeply nested token headers
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security <prodsec-ir-bot>
Status: NEW --- QA Contact:
Severity: medium Docs Contact:
Priority: medium    
Version: unspecifiedCC: akhatavk, alinfoot, amctagga, anpicker, anthomas, aoconnor, aos-team-art-private, aprice, asdas, bbrownin, blitton, bniver, bparees, cahl, cmyers, dfreiber, dkeler, dnakabaa, doconnor, dpaolell, dranck, drow, dschmidt, dtrifiro, eborisov, ebourniv, eglynn, ehelms, flucifre, ggainey, gmeno, groman, hasun, ikhan, ilpinto, jburrell, jdelft, jfula, jjoyce, jlanda, jmitchel, jowilson, jpasqual, jpretori, jsamir, jschluet, jupierce, juwatts, jwong, kaycoth, kshier, lball, lbrazdil, lcouzens, lgarciaa, lhh, ljawale, ltomasbo, mbarnett, mbenjamin, mbiarnes, mburns, mdellweg, mgarciac, mhackett, mhayden, mhulan, mminar, msilmser, ngough, nmoumoul, nyancey, oezr, omaciel, ometelka, osousa, pcreech, ppalepu, ppostler, prdhamdh, ptisnovs, rbiba, rbobbitt, rchan, rekumar, rhel-process-autobot, rjohnson, sbunciak, sdoran, sghai, sidsharm, simaishi, smallamp, sostapov, sskracic, stcannon, suppawar, syedriko, thason, tmalecek, tpfromme, ttakamiy, vereddy, veshanka, vkumar, vlaad, vvoronko, watson-tool-maintainers, weaton, xdharmai, yguenane, ykashtan
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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Doc Text:
A flaw was found in PyJWT. An unauthenticated remote attacker could trigger a Denial of Service (DoS) condition by supplying a specially crafted JSON Web Token (JWT) with deeply nested headers during decoding. Processing these nested structures causes an uncaught recursion error that bypasses standard error handling, leading to request-level failures and potential application crashes.
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Description OSIDB Bzimport 2026-09-28 21:03:19 UTC
PyJWT is a Python implementation of JSON Web Token standards. From 2.13.0 until 2.14.0, PyJWS._load in jwt/api_jws.py is affected because parser catches ValueError but not RecursionError. This occurs when a deeply nested token header reaches json.loads. As a result, RecursionError escapes the documented PyJWT error hierarchy. Consequently, an unauthenticated malformed token can cause a request-level failure and HTTP 500. This issue is fixed in version 2.14.0.