Linux: Off-by-one Error
CVE-2026-53036 is a high-severity off-by-one error vulnerability in Linux, with a CVSS 3.1 base score of 7.8 out of 10. It can be exploited with local access to the system by an attacker with a low-privileged account, without any action from a user. The record lists versions a5dfeb3b61065039488342d43ae06d4729d955d4, 7fd3b41260c6120e7b60164afea5d961af6224f9, 6927f0d6794aa73318bbfa929f1ff6065b0620df as the first without the flaw, so updating Linux to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.14% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Linux to a5dfeb3b61065039488342d43ae06d4729d955d4 or 7fd3b41260c6120e7b60164afea5d961af6224f9 or 6927f0d6794aa73318bbfa929f1ff6065b0620df or 1a113b5497297871699cd498b1b83542e0db7f15, whichever matches your release line, or a later version.
- Update Linux Kernel to 6.1.175 or 6.6.141 or 6.12.91 or 6.18.33, whichever matches your release line, or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Linux | Linux | e54bcde3d69d40023ae77727213d14f920eb264a up to, but not including, a5dfeb3b61065039488342d43ae06d4729d955d4; e54bcde3d69d40023ae77727213d14f920eb264a up to, but not including, 7fd3b41260c6120e7b60164afea5d961af6224f9; e54bcde3d69d40023ae77727213d14f920eb264a up to, but not including, 6927f0d6794aa73318bbfa929f1ff6065b0620df; e54bcde3d69d40023ae77727213d14f920eb264a up to, but not including, 1a113b5497297871699cd498b1b83542e0db7f15; e54bcde3d69d40023ae77727213d14f920eb264a up to, but not including, fb74defa1cca1a73177c0c761e641332e4f979a3; e54bcde3d69d40023ae77727213d14f920eb264a up to, but not including, 1dd8be4ec722ce54e4cace59f3a4ba658111b3ec; 3.18 | a5dfeb3b61065039488342d43ae06d4729d955d4, 7fd3b41260c6120e7b60164afea5d961af6224f9, 6927f0d6794aa73318bbfa929f1ff6065b0620df, 1a113b5497297871699cd498b1b83542e0db7f15, fb74defa1cca1a73177c0c761e641332e4f979a3, 1dd8be4ec722ce54e4cace59f3a4ba658111b3ec |
| Linux | Linux Kernel | 3.18 up to, but not including, 6.1.175; 6.2 up to, but not including, 6.6.141; 6.7 up to, but not including, 6.12.91; 6.13 up to, but not including, 6.18.33; 6.19 up to, but not including, 7.0.10 | 6.1.175, 6.6.141, 6.12.91, 6.18.33, 7.0.10 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- LocalThe attacker needs local access or must trick a user into running something.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H. Scored by CNA.
Official description
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.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Off-by-one Error
A product calculates or uses an incorrect maximum or minimum value that is 1 more, or 1 less, than the correct value.
How developers prevent this class of flaw
- When copying character arrays or using character manipulation methods, the correct size parameter must be used to account for the null terminator that needs to be added at the end of the array. Some examples of functions susceptible to this weakness in C include strcpy(), strncpy(), strcat(), strncat(), printf(), sprintf(), scanf() and sscanf().
Timeline
- CVE record published.
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- git.kernel.org/stable/c/1a113b5497297871699cd498b1b83542e0db7f15
- git.kernel.org/stable/c/1dd8be4ec722ce54e4cace59f3a4ba658111b3ec
- git.kernel.org/stable/c/6927f0d6794aa73318bbfa929f1ff6065b0620df
- git.kernel.org/stable/c/7fd3b41260c6120e7b60164afea5d961af6224f9
- git.kernel.org/stable/c/a5dfeb3b61065039488342d43ae06d4729d955d4
- git.kernel.org/stable/c/fb74defa1cca1a73177c0c761e641332e4f979a3
Recent Off-by-one Error vulnerabilities
- 9.8 Critical severity
- 7.8 High severity
- 8.6 High severity
- 7.8 High severity
- 8.6 High severity
- 7.5 High severity
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