EUVD-2026-59327
GHSA-xwq5-6xrg-83hr
Lifecycle Timeline
2DescriptionCVE.org
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[].
Analysis
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[].
Same technique Information Disclosure
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External POC / Exploit Code
Leaving vuln.today