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CVE-2026-53036

bpf, arm64: Fix off-by-one in check_imm signed range check PUBLISHED

Description (CNA)

In the Linux kernel, the following vulnerability has been resolved: bpf, arm64: Fix off-by-one in check_imm signed range check check_imm(bits, imm) is used in the arm64 BPF JIT to verify that a branch displacement (in arm64 instruction units) fits into the signed N-bit immediate field of a B, B.cond or CBZ/CBNZ encoding before it is handed to the encoder. The macro currently tests for (imm > 0 && imm >> bits) || (imm < 0 && ~imm >> bits) which admits values in [-2^N, 2^N) — effectively a signed (N+1)-bit range. A signed N-bit field only holds [-2^(N-1), 2^(N-1)), so the check admits one extra bit of range on each side. In particular, for check_imm19(), values in [2^18, 2^19) slip past the check but do not fit into the 19-bit signed imm19 field of B.cond. aarch64_insn_encode_immediate() then masks the raw value into the 19-bit field, setting bit 18 (the sign bit) and flipping a forward branch into a backward one. Same class of issue exists for check_imm26() and the B/BL encoding. Shift by (bits - 1) instead of bits so the actual signed N-bit range is enforced.

Affected (CNA)

Vendor / productVersions
Linux / Linuxaffected e54bcde3d69d40023ae77727213d14f920eb264a before a5dfeb3b61065039488342d43ae06d4729d955d4; affected e54bcde3d69d40023ae77727213d14f920eb264a before 7fd3b41260c6120e7b60164afea5d961af6224f9; affected e54bcde3d69d40023ae77727213d14f920eb264a before 6927f0d6794aa73318bbfa929f1ff6065b0620df; affected e54bcde3d69d40023ae77727213d14f920eb264a before 1a113b5497297871699cd498b1b83542e0db7f15; affected e54bcde3d69d40023ae77727213d14f920eb264a before fb74defa1cca1a73177c0c761e641332e4f979a3; affected e54bcde3d69d40023ae77727213d14f920eb264a before 1dd8be4ec722ce54e4cace59f3a4ba658111b3ec
Linux / Linuxaffected 3.18; unaffected 0 before 3.18; unaffected 6.1.175 through 6.1.*; unaffected 6.6.141 through 6.6.*; unaffected 6.12.91 through 6.12.*; unaffected 6.18.33 through 6.18.*; unaffected 7.0.10 through 7.0.*; unaffected 7.1 through *

CWE

No CWE identifiers supplied.

References