Linux Kernel up to 6.18.39/7.1.4 BPF cgroup backward compat bpf_mprog_query uattr_size out-of-bounds write

CVSS Meta Temp Score
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CTI Interest Score
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8.7$5k-$25k0.47

Summaryinfo

A vulnerability was found in Linux Kernel up to 6.18.39/7.1.4 and classified as very critical. This vulnerability affects the function bpf_mprog_query of the component BPF cgroup backward compat. Such manipulation of the argument uattr_size leads to out-of-bounds write. This vulnerability is listed as CVE-2026-74371. The attack may be performed from remote. There is no available exploit.

Detailsinfo

A vulnerability was found in Linux Kernel up to 6.18.39/7.1.4. It has been rated as very critical. Affected by this issue is the function bpf_mprog_query of the component BPF cgroup backward compat. The manipulation of the argument uattr_size with an unknown input leads to a out-of-bounds write vulnerability. Using CWE to declare the problem leads to CWE-787. The product writes data past the end, or before the beginning, of the intended buffer. Impacted is confidentiality, integrity, and availability. CVE summarizes:

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.

The advisory is available at git.kernel.org. This vulnerability is handled as CVE-2026-74371 since 08/15/2026. The exploitation is known to be easy. The attack may be launched remotely. Additional levels of successful authentication are necessary for exploitation. Technical details are known, but there is no available exploit. The structure of the vulnerability defines a possible price range of USD $5k-$25k at the moment (estimation calculated on 08/15/2026).

Upgrading to version 6.18.40, 7.1.5 or 7.2-rc1 eliminates this vulnerability. Applying the patch a7131340d0f95df9a541257dccab5d85e6bcdd2b/d3d630e8a7f3421bc2d204b87bdff35b4432a8e3/21c4b99b27f3f85b89256e81b3e997dec0a460d0 is able to eliminate this problem.

If you want to get best quality of vulnerability data, you may have to visit VulDB.

Productinfo

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Vendor

Name

Version

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Website

CPE 2.3info

CPE 2.2info

CVSSv4info

VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv3info

VulDB Meta Base Score: 9.1
VulDB Meta Temp Score: 8.7

VulDB Base Score: 9.1
VulDB Temp Score: 8.7
VulDB Vector: 🔒
VulDB Reliability: 🔍

CVSSv2info

AVACAuCIA
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💳💳💳💳💳💳
💳💳💳💳💳💳
VectorComplexityAuthenticationConfidentialityIntegrityAvailability
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VulDB Base Score: 🔒
VulDB Temp Score: 🔒
VulDB Reliability: 🔍

Exploitinginfo

Class: Out-of-bounds write
CWE: CWE-787 / CWE-119
CAPEC: 🔒
ATT&CK: 🔒

Physical: No
Local: No
Remote: Yes

Availability: 🔒
Status: Not defined
Price Prediction: 🔍
Current Price Estimation: 🔒

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Threat Intelligenceinfo

Interest: 🔍
Active Actors: 🔍
Active APT Groups: 🔍

Countermeasuresinfo

Recommended: Upgrade
Status: 🔍

0-Day Time: 🔒

Upgrade: Kernel 6.18.40/7.1.5/7.2-rc1
Patch: a7131340d0f95df9a541257dccab5d85e6bcdd2b/d3d630e8a7f3421bc2d204b87bdff35b4432a8e3/21c4b99b27f3f85b89256e81b3e997dec0a460d0

Timelineinfo

08/15/2026 Advisory disclosed
08/15/2026 +0 days CVE reserved
08/15/2026 +0 days VulDB entry created
08/15/2026 +0 days VulDB entry last update

Sourcesinfo

Vendor: kernel.org

Advisory: git.kernel.org
Status: Confirmed

CVE: CVE-2026-74371 (🔒)
GCVE (CVE): GCVE-0-2026-74371
GCVE (VulDB): GCVE-100-390338

Entryinfo

Created: 08/15/2026 10:04
Changes: 08/15/2026 10:04 (60)
Complete: 🔍
Cache ID: 216::103

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