bpf: reject negative CO-RE accessor indices in bpf_core_parse_spec()

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: reject negative CO-RE accessor indices in bpf_core_parse_spec() CO-RE accessor strings are colon-separated indices that describe a path from a root BTF type to a target field, e.g. "0:1:2" walks through nested struct members. bpf_core_parse_spec() parses each component with sscanf("%d"), so negative values like -1 are silently accepted. The subsequent bounds checks (access_idx >= btf_vlen(t)) only guard the upper bound and always pass for negative values because C integer promotion converts the __u16 btf_vlen result to int, making the comparison (int)(-1) >= (int)(N) false for any positive N. When -1 reaches btf_member_bit_offset() it gets cast to u32 0xffffffff, producing an out-of-bounds read far past the members array. A crafted BPF program with a negative CO-RE accessor on any struct that exists in vmlinux BTF (e.g. task_struct) crashes the kernel deterministically during BPF_PROG_LOAD on any system with CONFIG_DEBUG_INFO_BTF=y (default on major distributions). The bug is reachable with CAP_BPF: BUG: unable to handle page fault for address: ffffed11818b6626 #PF: supervisor read access in kernel mode #PF: error_code(0x0000) - not-present page Oops: Oops: 0000 [#1] SMP KASAN NOPTI CPU: 0 UID: 0 PID: 85 Comm: poc Not tainted 7.0.0-rc6 #18 PREEMPT(full) RIP: 0010:bpf_core_parse_spec (tools/lib/bpf/relo_core.c:354) RAX: 00000000ffffffff Call Trace: <TASK> bpf_core_calc_relo_insn (tools/lib/bpf/relo_core.c:1321) bpf_core_apply (kernel/bpf/btf.c:9507) check_core_relo (kernel/bpf/verifier.c:19475) bpf_check (kernel/bpf/verifier.c:26031) bpf_prog_load (kernel/bpf/syscall.c:3089) __sys_bpf (kernel/bpf/syscall.c:6228) </TASK> CO-RE accessor indices are inherently non-negative (struct member index, array element index, or enumerator index), so reject them immediately after parsing.

Timeline

Scores

EPSS (exploitation in 30 days)

0.14% · top 97% of all CVEs (11 Nov 2026)

The list uses the assigner's score when there is one, then CISA's, then NVD's: High 7.8.

Affected products

• Linux · Linux

  • affected ddc7c3042614e273044f698d2beab25cc3842d45 – < c8e49b79c4b48bd687706ff6e9c82638dc81ef80
  • affected ddc7c3042614e273044f698d2beab25cc3842d45 – < a9e777f856cd2f1efc106afc7bf21aef868509d5
  • affected ddc7c3042614e273044f698d2beab25cc3842d45 – < 669349b4612c26b3d7aacfa99d7174681bd19223
  • affected ddc7c3042614e273044f698d2beab25cc3842d45 – < 3ff85ae79e1a74baeb916b78a63d821f6d19a994
  • affected ddc7c3042614e273044f698d2beab25cc3842d45 – < 36a9012f76ba8d9189ae56a1f8bb7c87c07a1f3a
  • affected ddc7c3042614e273044f698d2beab25cc3842d45 – < 76f2ebaf79a9ae6d0737b87f045fe769e425d78f
  • affected ddc7c3042614e273044f698d2beab25cc3842d45 – < 99dbab7b5a12d8f58d5b0aa2f7a1fe656a70f4b2
  • affected ddc7c3042614e273044f698d2beab25cc3842d45 – < 1c22483a2c4bbf747787f328392ca3e68619c4dc

• Linux · Linux

  • affected 5.4
  • unaffected < 5.4
  • unaffected 5.10.267 – ≤ 5.10.*
  • unaffected 5.15.209 – ≤ 5.15.*
  • unaffected 6.1.175 – ≤ 6.1.*
  • unaffected 6.6.141 – ≤ 6.6.*
  • unaffected 6.12.91 – ≤ 6.12.*
  • unaffected 6.18.33 – ≤ 6.18.*
  • unaffected 7.0.10 – ≤ 7.0.*
  • unaffected 7.1 – ≤ *

Sources

The same CVE in the primary databases and aggregators, to check against.

• CVE.org record (opens in a new tab)
• CVE List JSON (GitHub) (opens in a new tab)
• NVD (opens in a new tab)
• FIRST EPSS (opens in a new tab)
• EUVD EUVD-2026-32165 (opens in a new tab)
• OSV.dev (opens in a new tab)
• GitHub Advisories (opens in a new tab)
• CIRCL Vulnerability-Lookup (opens in a new tab)

Badge for a README or a ticket

[![CVE-2026-45839](https://cveledger.app/badge/CVE-2026-45839.svg)](https://cveledger.app/cve/CVE-2026-45839)

Record last updated 15 Oct 2026, 01:19 UTC.