Bug 2501881 (CVE-2026-49852)

Summary:	CVE-2026-49852 joserfc: joserfc: Integrity bypass via forged HMAC-signed tokens
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security <prodsec-ir-bot>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	anpicker, anthomas, bparees, 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, rchan, rjohnson, sbunciak, sdoran, simaishi, smallamp, stcannon, suppawar, syedriko, teagle, thason, tmalecek, ttakamiy, vkumar, xdharmai, yguenane, ykashtan
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in the joserfc Python library. A remote attacker can exploit a vulnerability in the `joserfc.jwt.decode` function to forge HMAC-signed tokens. This occurs because the library accepts tokens signed with an empty or null verification key, allowing an attacker to bypass integrity checks. Successful exploitation could lead to an integrity compromise of data processed by the library.	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:

Description OSIDB Bzimport 2026-07-17 20:02:05 UTC

joserfc is a Python library that provides an implementation of several JSON Object Signing and Encryption (JOSE) standards. Prior to 1.6.8, joserfc.jwt.decode accepts attacker-forged HMAC-signed tokens when the caller-supplied verification key is the empty string or None, because HMACAlgorithm.sign and HMACAlgorithm.verify in src/joserfc/_rfc7518/jws_algs.py pass the output of OctKey.get_op_key(...) to hmac.new(...) and OctKey.import_key in src/joserfc/_rfc7518/oct_key.py only emits a SecurityWarning for keys shorter than 14 bytes without rejecting zero-length input. This issue is fixed in version 1.6.8.