CVE-2026-98034

Published: September 29, 2026Last modified: September 29, 2026

Description

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.

Status

References

• https://git.kernel.org/stable/c/86168208737bdd267d92d855d453d1d2f840df19
• https://git.kernel.org/stable/c/ecdc5043794c9184aa8e6c814603899479c46b35