CVE-2026-72428: bpf: Fix stack slot index in nospec checks

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: 2026-08-15 · updated 2026-08-17

Description

In the Linux kernel, the following vulnerability has been resolved: bpf: Fix stack slot index in nospec checks check_stack_write_fixed_off() computes the byte slot for a fixed-offset stack write as -off - 1, and records each written byte in slot_type[] with (slot - i) % BPF_REG_SIZE. The Spectre v4 sanitization pre-check uses slot_type[i] instead. For a 4-byte write at fp-8 after the lower half of fp-8 has been zeroed, the pre-check scans bytes 0..3 and sees STACK_ZERO while the actual write updates bytes 7..4. That can leave the second half-slot write without nospec_result even though the bytes being overwritten still require sanitization. Use the same slot index in the sanitization pre-check that the write path uses when updating slot_type[].

Affected products

Linux kernel: from 5.10.56 before 5.10.261; from 4.19.207 before 4.20; from 5.4.146 before 5.5; from 5.13.8 before 5.14; 5.14 — fixed in 4.20, 5.10.261, 5.14, 5.5, 7.2

How to fix

Upgrade to a fixed version: Linux kernel 4.20, 5.10.261, 5.14, 5.5. Check the vendor advisory for mitigations.

References

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