In the Linux kernel, the following vulnerability has been resolved: bpf: Fix incorrect pruning due to atomic fetch precision tracking When backtrack_insn encounters a BPF_STX instruction with BPF_ATOMIC and BPF_FETCH, the src register (or r0 for BPF_CMPXCHG) also acts as a destination, thus receiving the old value from the memory location. The current backtracking logic does not account for this. It treats atomic fetch operations the same as regular stores where the src register is only an input. This leads the backtrack_insn to fail to propagate precision to the stack location, which is then not marked as precise! Later, the verifier's path pruning can incorrectly consider two states equivalent when they differ in terms of stack state. Meaning, two branches can be treated as equivalent and thus get pruned when they should not be seen as such. Fix it as follows: Extend the BPF_LDX handling in backtrack_insn to also cover atomic fetch operations via is_atomic_fetch_insn() helper. When the fetch dst register is being tracked for precision, clear it, and propagate precision over to the stack slot. For non-stack memory, the precision walk stops at the atomic instruction, same as regular BPF_LDX. This covers all fetch variants. Before: 0: (b7) r1 = 8 ; R1=8 1: (7b) *(u64 *)(r10 -8) = r1 ; R1=8 R10=fp0 fp-8=8 2: (b7) r2 = 0 ; R2=0 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) ; R2=8 R10=fp0 fp-8=mmmmmmmm 4: (bf) r3 = r10 ; R3=fp0 R10=fp0 5: (0f) r3 += r2 mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1 mark_precise: frame0: regs=r2 stack= before 4: (bf) r3 = r10 mark_precise: frame0: regs=r2 stack= before 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) mark_precise: frame0: regs=r2 stack= before 2: (b7) r2 = 0 6: R2=8 R3=fp8 6: (b7) r0 = 0 ; R0=0 7: (95) exit After: 0: (b7) r1 = 8 ; R1=8 1: (7b) *(u64 *)(r10 -8) = r1 ; R1=8 R10=fp0 fp-8=8 2: (b7) r2 = 0 ; R2=0 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) ; R2=8 R10=fp0 fp-8=mmmmmmmm 4: (bf) r3 = r10 ; R3=fp0 R10=fp0 5: (0f) r3 += r2 mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1 mark_precise: frame0: regs=r2 stack= before 4: (bf) r3 = r10 mark_precise: frame0: regs=r2 stack= before 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) mark_precise: frame0: regs= stack=-8 before 2: (b7) r2 = 0 mark_precise: frame0: regs= stack=-8 before 1: (7b) *(u64 *)(r10 -8) = r1 mark_precise: frame0: regs=r1 stack= before 0: (b7) r1 = 8 6: R2=8 R3=fp8 6: (b7) r0 = 0 ; R0=0 7: (95) exit

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - bpf: Fix incorrect pruning due to atomic fetch precision tracking When backtrack_insn encounters a BPF_STX     instruction with BPF_ATOMIC and BPF_FETCH, the src register (or r0 for BPF_CMPXCHG) also acts as a     destination, thus receiving the old value from the memory location. The current backtracking logic does     not account for this. It treats atomic fetch operations the same as regular stores where the src register     is only an input. This leads the backtrack_insn to fail to propagate precision to the stack location,     which is then not marked as precise! Later, the verifier's path pruning can incorrectly consider two     states equivalent when they differ in terms of stack state. Meaning, two branches can be treated as     equivalent and thus get pruned when they should not be seen as such. Fix it as follows: Extend the BPF_LDX     handling in backtrack_insn to also cover atomic fetch operations via is_atomic_fetch_insn() helper. When     the fetch dst register is being tracked for precision, clear it, and propagate precision over to the stack     slot. For non-stack memory, the precision walk stops at the atomic instruction, same as regular BPF_LDX.
    This covers all fetch variants. Before: 0: (b7) r1 = 8 ; R1=8 1: (7b) *(u64 *)(r10 -8) = r1 ; R1=8 R10=fp0     fp-8=8 2: (b7) r2 = 0 ; R2=0 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) ; R2=8 R10=fp0     fp-8=mmmmmmmm 4: (bf) r3 = r10 ; R3=fp0 R10=fp0 5: (0f) r3 += r2 mark_precise: frame0: last_idx 5     first_idx 0 subseq_idx -1 mark_precise: frame0: regs=r2 stack= before 4: (bf) r3 = r10 mark_precise:
    frame0: regs=r2 stack= before 3: (db) r2 = atomic64_fetch_add((u64 *)(r10 -8), r2) mark_precise: frame0:
    regs=r2 stack= before 2: (b7) r2 = 0 6: R2=8 R3=fp8 6: (b7) r0 = 0 ; R0=0 7: (95) exit After: 0: (b7) r1 =     8 ; R1=8 1: (7b) *(u64 *)(r10 -8) = r1 ; R1=8 R10=fp0 fp-8=8 2: (b7) r2 = 0 ; R2=0 3: (db) r2 =     atomic64_fetch_add((u64 *)(r10 -8), r2) ; R2=8 R10=fp0 fp-8=mmmmmmmm 4: (bf) r3 = r10 ; R3=fp0 R10=fp0 5:
    (0f) r3 += r2 mark_precise: frame0: last_idx 5 first_idx 0 subseq_idx -1 mark_precise: frame0: regs=r2     stack= before 4: (bf) r3 = r10 mark_precise: frame0: regs=r2 stack= before 3: (db) r2 =     atomic64_fetch_add((u64 *)(r10 -8), r2) mark_precise: frame0: regs= stack=-8 before 2: (b7) r2 = 0     mark_precise: frame0: regs= stack=-8 before 1: (7b) *(u64 *)(r10 -8) = r1 mark_precise: frame0: regs=r1     stack= before 0: (b7) r1 = 8 6: R2=8 R3=fp8 6: (b7) r0 = 0 ; R0=0 7: (95) exit (CVE-2026-43009)

Note that Nessus relies on the presence of the package as reported by the vendor.

ID	Name	Product	Family	Severity
320429	openSUSE 16 Security Update : kernel (openSUSE-SU-2026:20912-1)	Nessus	SuSE Local Security Checks	medium
319659	SUSE SLES16 Security Update : kernel (SUSE-SU-2026:21845-1)	Nessus	SuSE Local Security Checks	high
318240	SUSE SLES16 Security Update : kernel (SUSE-SU-2026:21860-1)	Nessus	SuSE Local Security Checks	high
318102	openSUSE 16 Security Update : kernel (openSUSE-SU-2026:20826-1)	Nessus	SuSE Local Security Checks	high
311692	Linux Distros Unpatched Vulnerability : CVE-2026-43009	Nessus	Misc.	high

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