Bug 2523102 (CVE-2026-75509)

Summary: CVE-2026-75509 joserfc: joserfc: Issuer-validation bypass via array-valued claims
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: anpicker, anthomas, dfreiber, dkeler, drow, dschmidt, ebourniv, ehelms, ggainey, hasun, ilpinto, jburrell, jfula, jlanda, jowilson, jpasqual, juwatts, jwong, kaycoth, kshier, ltomasbo, mdellweg, mhayden, mhulan, nmoumoul, nyancey, omaciel, ometelka, osousa, pcreech, ptisnovs, rbobbitt, rchan, rjohnson, sbunciak, sdoran, simaishi, smallamp, stcannon, suppawar, syedriko, thason, tmalecek, vkumar, xdharmai, yguenane, ykashtan
Target Milestone: ---Keywords: Security
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Hardware: All   
OS: Linux   
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A flaw was found in joserfc, a Python library for JSON Object Signing and Encryption (JOSE) standards. A remote attacker could exploit a vulnerability in the JWTClaimsRegistry by crafting a JSON Web Token (JWT) with an array-valued issuer (iss) claim. This flaw allows the attacker to bypass the intended issuer validation, potentially leading to impersonation or unauthorized access.
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oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
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Description OSIDB Bzimport 2026-08-24 20:21:54 UTC
joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to version 1.7.3, JWTClaimsRegistry applies membership matching to list-valued iss and sub claims, allowing an array-valued iss that contains the expected issuer to pass an intended equality check and enabling issuer-validation bypass. This issue is fixed in version 1.7.3.