Bug 2482178 (CVE-2026-45927)

Summary:	CVE-2026-45927 kernel: bpf: Require frozen map for calculating map hash
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:	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 the Linux kernel's Berkeley Packet Filter (BPF) subsystem. This vulnerability, a Time-of-check to time-of-use (TOCTOU) bug, allows a local attacker to modify the contents of a BPF map after its hash has been calculated but before it is frozen. Consequently, a trusted loader could be deceived into verifying an outdated hash, leading to the loading of potentially malicious or unauthorized code. This could compromise the integrity of the system.	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 2026-05-27 15:14:59 UTC

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

bpf: Require frozen map for calculating map hash

Currently, bpf_map_get_info_by_fd calculates and caches the hash of the
map regardless of the map's frozen state.

This leads to a TOCTOU bug where userspace can call
BPF_OBJ_GET_INFO_BY_FD to cache the hash and then modify the map
contents before freezing.

Therefore, a trusted loader can be tricked into verifying the stale hash
while loading the modified contents.

Fix this by returning -EPERM if the map is not frozen when the hash is
requested. This ensures the hash is only generated for the final,
immutable state of the map.

Comment 1 Keith Grant 2026-05-28 00:56:54 UTC

Upstream advisory:
https://lore.kernel.org/linux-cve-announce/2026052726-CVE-2026-45927-e864@gregkh/T