bpf: Reject narrower access to pointer ctx fields

MITRE NVD CVE.ORG JSON API

Summary

CVECVE-2025-38591
StatePUBLISHED
AssignerLinux
Source PriorityCVE Program / NVD first with legacy fallback
Published2025-08-19 17:15:36 UTC
Updated2026-07-14 13:17:41 UTC
DescriptionIn the Linux kernel, the following vulnerability has been resolved: bpf: Reject narrower access to pointer ctx fields The following BPF program, simplified from a syzkaller repro, causes a kernel warning: r0 = *(u8 *)(r1 + 169); exit; With pointer field sk being at offset 168 in __sk_buff. This access is detected as a narrower read in bpf_skb_is_valid_access because it doesn't match offsetof(struct __sk_buff, sk). It is therefore allowed and later proceeds to bpf_convert_ctx_access. Note that for the "is_narrower_load" case in the convert_ctx_accesses(), the insn->off is aligned, so the cnt may not be 0 because it matches the offsetof(struct __sk_buff, sk) in the bpf_convert_ctx_access. However, the target_size stays 0 and the verifier errors with a kernel warning: verifier bug: error during ctx access conversion(1) This patch fixes that to return a proper "invalid bpf_context access off=X size=Y" error on the load instruction. The same issue affects multiple other fields in context structures that allow narrow access. Some other non-affected fields (for sk_msg, sk_lookup, and sockopt) were also changed to use bpf_ctx_range_ptr for consistency. Note this syzkaller crash was reported in the "Closes" link below, which used to be about a different bug, fixed in commit fce7bd8e385a ("bpf/verifier: Handle BPF_LOAD_ACQ instructions in insn_def_regno()"). Because syzbot somehow confused the two bugs, the new crash and repro didn't get reported to the mailing list.

Risk And Classification

Primary CVSS: v3.1 5.5 MEDIUM from [email protected]

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

EPSS: 0.001800000 probability, percentile 0.076820000 (date 2026-07-14)

Problem Types: NVD-CWE-noinfo

CVSS v3.1 Breakdown

Attack Vector
Local
Attack Complexity
Low
Privileges Required
Low
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H

NVD Known Affected Configurations (CPE 2.3)

TypeVendorProductVersionUpdateEditionLanguage
Operating System Linux Linux Kernel All All All All

Vendor Declared Affected Products

SourceVendorProductVersionPlatforms
CNA Linux Linux affected f96da09473b52c09125cc9bf7d7d4576ae8229e0 7847c4140e06f6e87229faae22cc38525334c156 git Not specified
CNA Linux Linux affected f96da09473b52c09125cc9bf7d7d4576ae8229e0 feae34c992eb7191862fb1594c704fbbf650fef8 git Not specified
CNA Linux Linux affected f96da09473b52c09125cc9bf7d7d4576ae8229e0 33660d44e789edb4f303210c813fc56d56377a90 git Not specified
CNA Linux Linux affected f96da09473b52c09125cc9bf7d7d4576ae8229e0 058a0da4f6d916a79b693384111bb80a90d73763 git Not specified
CNA Linux Linux affected f96da09473b52c09125cc9bf7d7d4576ae8229e0 202900ceeef67458c964c2af6e1427c8e533ea7c git Not specified
CNA Linux Linux affected f96da09473b52c09125cc9bf7d7d4576ae8229e0 e09299225d5ba3916c91ef70565f7d2187e4cca0 git Not specified
CNA Linux Linux affected 4.13 Not specified
CNA Linux Linux unaffected 4.13 semver Not specified
CNA Linux Linux unaffected 5.10.249 5.10.* semver Not specified
CNA Linux Linux unaffected 5.15.199 5.15.* semver Not specified
CNA Linux Linux unaffected 6.1.162 6.1.* semver Not specified
CNA Linux Linux unaffected 6.12.67 6.12.* semver Not specified
CNA Linux Linux unaffected 6.16.1 6.16.* semver Not specified
CNA Linux Linux unaffected 6.17 * original_commit_for_fix Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP affected V3.1.6 * custom Not specified
ADP Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP affected V3.1.6 * custom Not specified

References

ReferenceSourceLinkTags
git.kernel.org/stable/c/33660d44e789edb4f303210c813fc56d56377a90 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/feae34c992eb7191862fb1594c704fbbf650fef8 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/058a0da4f6d916a79b693384111bb80a90d73763 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/e09299225d5ba3916c91ef70565f7d2187e4cca0 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
git.kernel.org/stable/c/7847c4140e06f6e87229faae22cc38525334c156 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
cert-portal.siemens.com/productcert/html/ssa-019113.html 0b142b55-0307-4c5a-b3c9-f314f3fb7c5e cert-portal.siemens.com
git.kernel.org/stable/c/202900ceeef67458c964c2af6e1427c8e533ea7c 416baaa9-dc9f-4396-8d5f-8c081fb06d67 git.kernel.org Patch
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