Bug 2463370 (CVE-2026-40355)

Summary:	CVE-2026-40355 krb5: MIT Kerberos 5: Denial of Service via NULL pointer dereference in NegoEx mechanism
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:	abokovoy, jrische, rhel-process-autobot, watson-tool-maintainers
Target Milestone:	---	Keywords:	Security
Target Release:	---
Hardware:	All
OS:	Linux
Whiteboard:
Fixed In Version:		Doc Type:	---
Doc Text:	A flaw was found in MIT Kerberos 5 (krb5). An unauthenticated remote attacker can exploit a NULL pointer dereference vulnerability by calling `gss_accept_sec_context()` on a system with a NegoEx mechanism registered. This can lead to the termination of the process, resulting in a Denial of Service (DoS).	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:	2463393, 2463394, 2463398
Bug Blocks:

Description OSIDB Bzimport 2026-04-28 07:02:08 UTC

In MIT Kerberos 5 (aka krb5) before 1.22.3, there is a NULL pointer dereference if an application calls gss_accept_sec_context() on a system with a NegoEx mechanism registered in /etc/gss/mech. An unauthenticated remote attacker can trigger this, causing the process to terminate in parse_nego_message.

Comment 4 errata-xmlrpc 2026-05-13 05:45:30 UTC

This issue has been addressed in the following products:

  Red Hat Enterprise Linux 8

Via RHSA-2026:16799 https://access.redhat.com/errata/RHSA-2026:16799