Vulnerability in Linux

[ Description ]Official description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix NULL-ptr-deref in btf_var_show() btf_var_show() calls btf_type_id_resolve() unconditionally, which dereferences btf->resolved_ids. That is NULL for a base BTF - e.g. the vmlinux BTF that bpf_snprintf_btf() renders against - since base BTF is not resolved during parsing. btf_modifier_show() guards this with 'if (btf->resolved_ids)', but btf_var_show() does not. A BPF program that passes the type_id of a BTF_KIND_VAR from the vmlinux BTF to bpf_snprintf_btf() thus NULL-derefs: KASAN: probably user-memory-access in range [0x46638-0x4663f] RIP: 0010:btf_var_show (kernel/bpf/btf.c:2929) Call Trace: <TASK> btf_type_show (kernel/bpf/btf.c:8259) btf_type_snprintf_show (kernel/bpf/btf.c:8329) bpf_snprintf_btf (kernel/trace/bpf_trace.c:1047) bpf_prog_test_run_raw_tp (net/bpf/test_run.c:829) __sys_bpf (kernel/bpf/syscall.c:4804) do_syscall_64 (arch/x86/entry/syscall_64.c:84) entry_SYSCALL_64_after_hwframe (arch/x86/entry/entry_64.S:121) </TASK> Resolve the var's type directly with btf_type_skip_modifiers() when resolved_ids is NULL, mirroring btf_modifier_show().

[ Fixes ]Fixes and patches

No fix or interim patch is linked from our sources yet. Check the vendor references below and limit exposure of affected systems until a fix is available.

[ Advisories ]Government CERT advisories

• CERT-FR9 Oct 2026CERTFR-2026-AVI-1289

  Multiple vulnerabilities in the Debian LTS Linux kernel Translated from French

  Multiple vulnerabilities have been discovered in the Debian LTS Linux kernel. Some of them allow an attacker to cause privilege escalation, a breach of data confidentiality and denial of service.

  CVE-2025-38237CVE-2025-39833CVE-2025-39925+1311 more CVEs
• CERT-FR2 Oct 2026CERTFR-2026-AVI-1253

  Multiple vulnerabilities in the Debian Linux kernel Translated from French

  Multiple vulnerabilities have been discovered in the Debian Linux kernel. Some of them allow an attacker to cause privilege escalation, a breach of data confidentiality and denial of service.

  CVE-2025-38237CVE-2025-39833CVE-2025-39925+1310 more CVEs
• BSI CERT-Bund24 Sep 2026WID-SEC-2026-3579

  Linux Kernel: Multiple vulnerabilities Translated from German

  CVE-2026-97615CVE-2026-97978CVE-2026-98127+590 more CVEs

[ References ]References

• git.kernel.org/stable/c/5403a383f52fc0905703b488f7c3db4b2447dc58
• git.kernel.org/stable/c/5756450c9a702da0efb4a993d0a6766b965736f3
• git.kernel.org/stable/c/aec0a9c1579eb9edf534960be592d09481bd7ac3
• git.kernel.org/stable/c/ca086264e98108b44fdf53971033811a48defe2b
• git.kernel.org/stable/c/e0d6a06171633d3ee3f7a39b57e5c845fb2b79f2
• git.kernel.org/stable/c/e472ae0d97865e2021ee668a13eab64013aebf23
• git.kernel.org/stable/c/e83fcbe3b5d4a1ffb0569bb7c280358065c6017a
• git.kernel.org/stable/c/ea383b3ea56979ce54c8aa88e6ec67164986c401