EUVD-2026-59518
GHSA-wg9f-h9hg-j36p
Severity by source
AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Local bpf() syscall access with low privileges required; no interaction needed; kernel OOB write enables memory corruption for full system compromise.
Primary rating from Vendor (Linux).
CVSS VectorVendor: Linux
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Lifecycle Timeline
5DescriptionCVE.org
In the Linux kernel, the following vulnerability has been resolved:
bpf: fix BPF_PROG_QUERY OOB write and cgroup backward compat
BPF_PROG_QUERY writes back the 'query.revision' field unconditionally to userspace. If userspace passes a smaller 'bpf_attr' structure (e.g. 40 bytes, which was the layout before the addition of 'query.revision'), the kernel performs an out-of-bounds write.
Fix this by propagating the user-provided attribute size 'uattr_size' down to the cgroup query handlers, and conditionally skipping writing the revision field to userspace when the provided buffer size is insufficient.
query.revision in bpf_mprog_query is structurally identical to the cgroup case: a late tail field, written unconditionally.
But the backward-compat hazard is not the same.
The min-historical-size test is per command, and bpf_mprog_query only serves attach types that were born with revision in the struct:
- tcx_prog_query -> BPF_TCX_INGRESS/EGRESS
- netkit_prog_query -> BPF_NETKIT_PRIMARY/PEER
tcx, netkit, the revision field, and bpf_mprog_query itself all landed in the same v6.6 merge window (053c8e1f235d added the mprog query API + revision; tcx in e420bed02507, netkit in 35dfaad7188c). There has never been a tcx/netkit BPF_PROG_QUERY userspace that doesn't know about revision. So for these commands the minimum legitimate struct already covers offset 56-64 - no old binary can be broken here.
Contrast with cgroup: BPF_PROG_QUERY on cgroup attach types shipped in 2017; revision write-back was bolted on years later (120933984460). That path has a real population of pre-revision callers.
AnalysisAI
Out-of-bounds write in the Linux kernel BPF subsystem allows a local low-privileged user to corrupt memory by issuing a BPF_PROG_QUERY syscall with an undersized bpf_attr buffer that omits the query.revision field introduced in v6.6. The cgroup attach-type code path is the primary hazard: BPF_PROG_QUERY on cgroup types shipped in 2017, and the revision write-back was added years later, creating a real population of legacy callers whose smaller buffers trigger the unconditional OOB write. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Exploitation requires local OS access with at least low-level privileges (CVSS PR:L) - specifically, the ability to invoke the bpf() syscall, which on most distributions requires either CAP_BPF, CAP_SYS_ADMIN, or kernel.unprivileged_bpf_disabled=0. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | CVSS 7.8 (AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H) correctly reflects local, low-complexity exploitation requiring low OS-level privileges with potential for full system compromise. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A local user on a shared Linux system - such as a CI runner participant, container tenant, or unprivileged service account - invokes the bpf() syscall with BPF_PROG_QUERY targeting a cgroup attach type, deliberately passing a bpf_attr buffer sized to the pre-v6.6 layout that omits the query.revision field. The kernel writes the revision value past the end of the caller's buffer, corrupting adjacent userspace memory in a layout the attacker can control to redirect execution or escalate privileges. … |
| Remediation | Upgrade to Linux kernel 6.18.40, 7.1.5, or 7.2-rc1 or later, which incorporate the three stable-tree fix commits (a7131340, d3d630e8, 21c4b99b) available at https://git.kernel.org/stable/c/a7131340d0f95df9a541257dccab5d85e6bcdd2b, https://git.kernel.org/stable/c/d3d630e8a7f3421bc2d204b87bdff35b4432a8e3, and https://git.kernel.org/stable/c/21c4b99b27f3f85b89256e81b3e997dec0a460d0. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, conduct an inventory of Linux systems and identify those using legacy BPF_PROG_QUERY implementations, especially cgroup-related code paths from 2017 forward. …
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Same technique Buffer Overflow
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