CVE-2026-98034
UnknownSummary
A vulnerability in the Linux kernel BPF verifier regarding stores to kptr fields was fixed. The function check_map_kptr_access() allowed a scalar store into an untrusted kptr field only when the register was known to be zero, but did not mark that register as precise. This could allow bypassing the verifier and writing attacker-controlled data into the kptr field.
Risk Assessment
The flaw allows bypassing the BPF verifier and potentially performing unauthorized operations on BTF ID pointers. It may lead to privilege escalation or kernel instability.
Recommendation
Update the Linux kernel to a version with the fix. Monitor systems that allow unprivileged users to load BPF programs.
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Original NVD description (English source)
In the Linux kernel, the following vulnerability has been resolved: bpf: Mark NULL kptr stores precise check_map_kptr_access() permits a scalar store into an untrusted kptr field only when the register is known to contain zero. Unlike other verifier checks whose outcome depends on a scalar value, it does not mark that register precise. A state checkpoint reached with an imprecise zero can therefore prune a second path that reaches the store with an arbitrary nonzero scalar. The program can write attacker-controlled bits into the kptr field and load them back as a PTR_TO_BTF_ID. Call mark_chain_precision() before accepting a known-zero register. This forces state equivalence to compare its scalar range and makes the verifier visit and reject a path carrying a nonzero value.
Vulnerability data from NVD (NIST) · CISA KEV · EPSS