Bug 2536695 (CVE-2026-90250)

Summary: CVE-2026-90250 kernel: bpf, cgroup: Fix storage null-ptr-deref after replacing prog
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedCC: akhatavk, 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   
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A flaw was found in the Linux kernel's BPF (Berkeley Packet Filter) cgroup storage mechanism. When replacing an existing BPF program with a new one that uses `BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE`, the system may fail to properly allocate and assign the necessary cgroup storage. This oversight can lead to a null-pointer dereference, causing a system panic and resulting in a Denial of Service (DoS).
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Description OSIDB Bzimport 2026-09-17 19:08:06 UTC 
In the Linux kernel, the following vulnerability has been resolved:

bpf, cgroup: Fix storage null-ptr-deref after replacing prog

Syzkaller reported a storage null-ptr-deref issue after replacing prog.
This occurs in the following scenario:
1. prog A, an empty prog, is attached to a cgrp.
2. prog B uses BPF_MAP_TYPE_PERCPU_CGROUP_STORAGE and calls the
   bpf_get_local_storage helper.
3. link_update is called to replace prog A with prog B.

The reason is that __cgroup_bpf_replace fails to alloc and assign the
required cgrp storage for the incoming replacement prog. Consequently,
the new prog inherits an uninit storage, leading to null-ptr-deref panic
when kick the new prog.

Fix this by rejecting a link update if new_prog's cgroup storage is
incompatible with link->prog.
Comment 1 gkamathe 2026-09-23 19:24:33 UTC 
Upstream advisory:
https://git.kernel.org/pub/scm/linux/security/vulns.git/plain/cve/published/2026/CVE-2026-90250.mbox