Bug 2524434 (CVE-2026-74753)

Summary:	CVE-2026-74753 kernel: perf: Reject exited events as group leaders
Product:	[Other] Security Response	Reporter:	OSIDB Bzimport <bzimport>
Component:	vulnerability	Assignee:	Product Security DevOps Team <prodsec-dev>
Status:	NEW ---	QA Contact:
Severity:	high	Docs Contact:
Priority:	high
Version:	unspecified	CC:	akhatavk, akito5623, aos-team-art-private, asdas, dpaolell, jdelft, jupierce, lgarciaa, mbiarnes, ppalepu, ppostler, prdhamdh, rhel-process-autobot, sghai, sidsharm, suppawar, vlaad, 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 the Linux kernel's performance monitoring (perf) subsystem. This vulnerability allows a local attacker to trigger a use-after-free condition by improperly handling exited events as group leaders. Successful exploitation could lead to a system crash, resulting in a denial of service (DoS), or potentially enable an attacker to escalate privileges.	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 2026-08-26 14:51:29 UTC

In the Linux kernel, the following vulnerability has been resolved:

perf: Reject exited events as group leaders

perf_event_remove_on_exec() sets remove-on-exec events to the EXIT state
and detaches their group relationships.  The event's file descriptor can
remain open, however, and perf_event_open() currently accepts that event
as a group leader because its early validation rejects only REVOKED and
DEAD events.

A new sibling can consequently be linked to the detached leader.  When
the leader is closed, perf_group_detach() observes that its
PERF_ATTACH_GROUP bit is already clear and skips the new sibling.  The
sibling then retains a group_leader pointer to the freed event.

Reject group leaders in the EXIT state.  Perform the check while holding
the shared context mutex so that an exec in the target task cannot detach
the leader between validation and group attachment.

[peterz: make the earlier test fully consistent]

Comment 1 gkamathe 2026-08-27 06:35:31 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026082600-CVE-2026-74753-9105@gregkh/T

Comment 3 Akiyoshi Kurita 2026-08-28 01:34:48 UTC

FYI, a public exploit / PoC for CVE-2026-74753 is now available.

Red Hat CVE:
https://access.redhat.com/security/cve/cve-2026-74753

Public exploit / PoC:
https://github.com/google/security-research/tree/2623550a891f51ba099fd3cec8f07c32d7e2fc61/pocs/linux/kernelctf/CVE-2026-74753_lts/exploit/lts-6.12.101

Upstream fix:
https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?id=fa091f46c3833fb22384f10eade2b4e1e1d0b278

The upstream CVE announcement currently does not list fixed 6.6 or 6.12 stable backports.

From reviewing the upstream fix, I could not identify an obvious practical runtime mitigation other than applying a kernel containing the fix.

Sharing this because a working public exploit is now available.