CVE-2025-38591bpf: Reject narrower access to pointer ctx fields
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In 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.
- CVSS
- 5.5 MEDIUM (v3.1, NVD)CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H
- Weakness (CWE)
- Not given
- Known exploited
- Not in CISA's KEV catalog
- EPSS (exploitation in the next 30 days)
- Not loaded for this CVE
- Assigned by
- Linux
- NVD analysis
- Modified
- Record last updated
- Oct 15, 2026
- First seen by InfoSec Signals
- Oct 15, 2026
Affected products
Linux Linux linux:linux (from the name) | from f96da09473b52c09125cc9bf7d7d4576ae8229e0 before 7847c4140e06f6e87229faae22cc38525334c156; from f96da09473b52c09125cc9bf7d7d4576ae8229e0 before feae34c992eb7191862fb1594c704fbbf650fef8; from f96da09473b52c09125cc9bf7d7d4576ae8229e0 before 33660d44e789edb4f303210c813fc56d56377a90; from f96da09473b52c09125cc9bf7d7d4576ae8229e0 before e2e9599f3503df7cf3569d2b6c50d5488fb59435; from f96da09473b52c09125cc9bf7d7d4576ae8229e0 before 058a0da4f6d916a79b693384111bb80a90d73763; from f96da09473b52c09125cc9bf7d7d4576ae8229e0 before 202900ceeef67458c964c2af6e1427c8e533ea7c; from f96da09473b52c09125cc9bf7d7d4576ae8229e0 before e09299225d5ba3916c91ef70565f7d2187e4cca0 | CNA record |
Siemens SIMATIC S7-1500 CPU 1518-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIMATIC S7-1500 CPU 1518F-4 PN/DP MFP siemens:simatic_s7_1500_cpu_1518f_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
Siemens SIPLUS S7-1500 CPU 1518-4 PN/DP MFP siemens:siplus_s7_1500_cpu_1518_4_pn_dp_mfp (from the name) | from V3.1.6 | CISA ADP |
linux linux_kernel linux:linux_kernel | from 4.13 before 6.16.1 | NVD |
References
- https://git.kernel.org/stable/c/7847c4140e06f6e87229faae22cc38525334c156patch
- https://git.kernel.org/stable/c/feae34c992eb7191862fb1594c704fbbf650fef8patch
- https://git.kernel.org/stable/c/33660d44e789edb4f303210c813fc56d56377a90patch
- https://git.kernel.org/stable/c/e2e9599f3503df7cf3569d2b6c50d5488fb59435
- https://git.kernel.org/stable/c/058a0da4f6d916a79b693384111bb80a90d73763patch
- https://git.kernel.org/stable/c/202900ceeef67458c964c2af6e1427c8e533ea7cpatch
- https://git.kernel.org/stable/c/e09299225d5ba3916c91ef70565f7d2187e4cca0patch
- https://cert-portal.siemens.com/productcert/html/ssa-019113.html
- https://cert-portal.siemens.com/productcert/html/ssa-457936.html
The CVE record on cve.org NVD's entry
The CVE record is authoritative. Products marked “from the name” were identified from the CNA's free-text names, not a CPE, and are matched less certainly. This product uses the NVD API but is not endorsed or certified by the NVD.