CVE-2026-98007: bpf: Reject non-scalar bpf_loop iteration counts

Severity: unknown
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-09-25 · updated 2026-10-19

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Reject non-scalar bpf_loop iteration counts bpf_loop() declares its nr_loops argument as ARG_ANYTHING. Privileged programs may pass pointer values to such arguments, so check_func_arg() lets a pointer-valued R1 reach the helper-specific checks. Since commit bb124da69c47 ("bpf: keep track of max number of bpf_loop callback iterations"), the verifier marks R1 precise and reads its upper bound to limit callback simulation. Precision backtracking only accepts scalar registers, so passing a pointer instead triggers the "backtracking misuse" verifier warning. Kernels with panic_on_warn enabled subsequently panic. Introduce ARG_SCALAR for helper arguments that only accept scalar values and use it for bpf_loop() nr_loops. Generic helper argument validation then rejects pointers before loop inlining and precision processing.

Affected products

Linux kernel: from 6.6.15 before 6.6.158; 6.7 — fixed in 6.6.158, 7.3

How to fix

Upgrade to a fixed version: Linux kernel 6.6.158, 7.3. Check the vendor advisory for mitigations.

References

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