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CVE-2026-92485
bpf: Fix WARNING in bpf_tracing_link_release
Published 2026-09-17 (31 days ago) by the Linux kernel CNA. Subsystem include/linux. Debian urgency: not yet assigned.
What to do, per Debian release
Debian's own status for CVE-2026-92485 in every release this site tracks, and what each one means in practice. Every status below is the one the Debian Security Team publishes for this CVE. source
| Release | Status | Version | What this means |
|---|---|---|---|
| Debian 12bookworm | vulnerable | 6.1.190-1 | No fix published anywhere yet, neither in Debian nor upstream for the series bookworm tracks. Watch the Debian tracker page for this CVE. Advisories for bookworm have historically landed a median of 23 days after publication. |
| Debian 13trixie | vulnerable | 6.12.113-1 | No fix published anywhere yet, neither in Debian nor upstream for the series trixie tracks. Watch the Debian tracker page for this CVE. Advisories for trixie have historically landed a median of 11 days after publication. |
| Debian 14forky | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
| Debian unstablesid | fixed | 7.2.6-1 | Update the kernel and reboot. Fixed in 7.2.6-1. A running kernel keeps the old code until the machine restarts. |
The vulnerability
What the bug is
The trampoline could be corrupted by the blindly 'tr->flags = BPF_TRAMP_F_TAIL_CALL_CTX' in verifier. 1. A fexit attached to a tail_call_reachable prog. 'tr->flags' became 'BPF_TRAMP_F_CALL_ORIG | BPF_TRAMP_F_TAIL_CALL_CTX'. And, the trampoline would poke the target prog's nop insn using jmp insn instead of call insn. 2. Another fexit loaded with the same tail_call_reachable prog target. 'tr->flags' became 'BPF_TRAMP_F_TAIL_CALL_CTX'. 3. Close the first fexit link. Due to no BPF_TRAMP_F_CALL_ORIG in 'tr->flags', the trampoline will fail to restore the prog's nop insn using call insn. [ 3.410719] WARNING: kernel/bpf/syscall.c:3551 at bpf_tracing_link_release+0x53/0x60, CPU#1: test_progs/98 ... [ 3.428793] bpf_link_free+0x58/0x130 [ 3.429293] bpf_link_release+0x23/0x30 Fix the warning by updating 'tr->flags' with '|=' and lock.
Where it lives
The fix touches these files. If the subsystem is one you do not use, the practical exposure is lower, though the package is still the vulnerable one.
include/linux/bpf.h
kernel/bpf/trampoline.c
kernel/bpf/verifier.c
- What this is
- BPF [CORE]MAINTAINERS section matched on include/linux/bpf* · bpf@vger.kernel.org · Maintained
Check it on the machine
grep -wE 'CONFIG_BPF|CONFIG_BPF_JIT' /boot/config-$(uname -r)Reads the booted kernel's own configuration, on the machine and nowhere else. =y is built in, =m is a module, and an is not set line means the code is not there.
Show whether Debian builds this, per release
Debian builds this, but not on every flavour. At least one release below builds the code on some of its kernel flavours and not on others, so the answer depends on the architecture and flavour installed.
- bookwormy
- trixie, forky, sidYnot built on s390x/s390x
- y
- built into the kernel image on every flavour - only a patch removes it
- Y
- built in where it is built at all; some flavours do not build it
- Build switches
- CONFIG_BPF, CONFIG_BPF_JIT
- Reads as
- all on means the file is compiled; any one off means it is not.
From the configuration Debian publishes for every kernel flavour it builds. It covers only the architectures Debian ships a linux-config package for, and nothing about a kernel you built yourself. Debian's own status above stays authoritative about the source package.MAINTAINERS kbuild Makefiles Debian linux-config packages
Signals
- Published
- 2026-09-17 (31 days ago)source
- CVSS
- 7.8 high
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:Hsource recompute it - Attack vector
- local (AV:L)source
- EPSS
- 0.17%, higher than 6.3% of all CVEssource
- CISA KEV
- not listedthe KEV catalogue
- Debian urgency
- not yet assignedsource
- Subsystem
- include/linux
Upstream fixes
The versions the CNA records as introducing and fixing this, and the commit for each. source
| Introduced | Fixed in | Commit |
|---|---|---|
| 6.7 | 6.18.57 | 094f0a895cf9 |
| 6.7 | 7.2.6 | 48a0209d8da0 |
| 6.7 | 7.3 | 61aaa8782bec |
| 6.1.72 | 0 | 0 |
| 6.5.12 | 0 | 0 |
| 6.6.2 | 0 | 0 |
Why the CNA scored it this way
Quoted from the kernel CNA's own scoring file, word for word. A highlighted metric carries the most severe value CVSS v3.1 defines for it, which is what pushes the score up. source
- AV:LAttack vector, local
- The trigger is local bpf() only: BPF_PROG_LOAD of a tail_call_reachable target plus two BPF_TRACE_FEXIT programs (check_attach_btf_id overwrites tr->flags), BPF_LINK_CREATE via bpf_tracing_prog_attach, then close() of the first link into bpf_tracing_link_release. No remote protocol carries the malformed state.
- AC:LAttack complexity, low
- After the first fexit attach, bpf_trampoline_update sets BPF_TRAMP_F_CALL_ORIG and bpf_arch_text_poke installs a JMP (bpf_trampoline_use_jmp). A second BPF_PROG_LOAD then does tr->flags = BPF_TRAMP_F_TAIL_CALL_CTX in check_attach_btf_id; closing the first link hits the JMP-vs-CALL mismatch. The attacker owns both loads and the close; CONFIG_DYNAMIC_FTRACE_WITH_JMP is def_bool y on x86_64.
- PR:LPrivileges required, low
- bpf_prog_load() of BPF_PROG_TYPE_TRACING/BPF_TRACE_FEXIT requires CAP_BPF and, via is_perfmon_prog_type(), CAP_PERFMON; bpf_token_capable() with a delegated BPF token grants those into a non-init user namespace, so this is not init-namespace root.
- UI:NUser interaction, none
- The attacker loads both fexit programs, attaches the first with BPF_LINK_CREATE/bpf_tracing_prog_attach, and closes that link fd themselves; no victim mount, open, or other action is required.
- S:UScope, unchanged
- The leftover JMP in the target program and the use-after-free of fexit1's JIT image stay inside host kernel BPF trampoline code; they do not cross a VM, IOMMU, or sandbox boundary.
- C:HConfidentiality impact, high
- Failed bpf_trampoline_unlink_prog() leaves the target's 5-byte slot as a JMP into the trampoline image that still calls fexit1->bpf_func, while bpf_link_free()→bpf_link_dealloc() immediately bpf_prog_put()s fexit1 (no dealloc_deferred). After bpf_jit_free(), later target invocations read that freed executable image.
- I:HIntegrity impact, high
- The same dangling trampoline CALL into fexit1's freed JIT pages is an executable use-after-free; the attacker controls the fexit program and can spray replacement JIT text at that address, hijacking kernel control flow when the target program runs.
- A:HAvailability impact, high
- bpf_tracing_link_release() WARN_ON_ONCE()s the failed bpf_trampoline_unlink_prog() after bpf_arch_text_poke() rejects the JMP-vs-CALL restore. Running the target afterward jumps to the trampoline and calls the freed fexit JIT, causing a kernel paging fault/oops.