# CVE-2026-54875: Non-Constant-Time SM2 Scalar Multiplication on ARM64 and RISC-V

CVE-2026-54875 is fixed in 4 products on 1 platform, first by libssl3t64 3.5.5-1ubuntu3.6, released September 28, 2026. It is not reported as exploited. Patch Radar priority: Routine.

- Web page: https://patchblox.com/security/cve/CVE-2026-54875
- Priority: Routine
- CVSS: 3.7 (Low)
- EPSS: 0.0048
- CISA KEV: not listed
- Exploited (vendor report): no
- Publicly disclosed: no
- Published: Sep 28, 2026
- Weakness: Observable Timing Discrepancy
- Vendor advisory: https://msrc.microsoft.com/update-guide/vulnerability/CVE-2026-54875

## Description

Issue summary: A non-constant-time optimized implementation of scalar point multiplication is used for SM2 private key operations on ARM64 and RISC-V platforms.  Impact summary: An attacker able to measure the time taken by, or to observe the cache-line access pattern of SM2 signing or decryption on an affected platform can learn information about the secret scalar.  CWE: CWE-208: Observable Timing Discrepancy  Description: On ARM64 and RISC-V processors, the SM2 curve uses an optimized scalar multiplication implementation whose conditional branches and table look ups are chosen according to the bits of the secret scalar. The execution time and the cache-access pattern therefore depend on the long-term private key (during SM2 decryption) or the per-signature nonce (during SM2 signature generation), forming a timing and cache side-channel.  FIPS Impact: no SM2 is not a FIPS algorithm and the optimized SM2 implementation is not part of the FIPS module.  OpenSSL 4.0, 3.6, 3.5 and 3.4 are vulnerable to this issue on AArch64 and RISC-V.  OpenSSL 3.0, 1.1.1 and 1.0.2 are not affected by this issue.  OpenSSL 4.0 users should upgrade to OpenSSL 4.0.3. OpenSSL 3.6 users should upgrade to OpenSSL 3.6.5. OpenSSL 3.5 users should upgrade to OpenSSL 3.5.9. OpenSSL 3.4 users should upgrade to OpenSSL 3.4.8.  This issue was reported on 2 May 2026 by Abhinav Agarwal. It was independently reported on 6 June 2026 by Feng Xue. The fix was developed by Igor Ustinov.  -- cut (non-publishing metadata for internal use) -- Reported by: Abhinav Agarwal, Feng Xue Fixed by: Igor Ustinov

## Where it's fixed

| Platform | Product | Fixed in | Fix | Released |
|---|---|---|---|---|
| Linux | libssl3t64 Ubuntu 26.04.1 LTS (resolute) | 3.5.5-1ubuntu3.6 | [libssl3t64 3.5.5-1ubuntu3.6](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-libssl3t64-3.5.5-1ubuntu3.6.md) | Sep 28, 2026 |
| Linux | openssl Debian 13.5 (trixie) | 3.5.7-1~deb13u3 | [DEBIAN-CVE-2026-54875](https://patchblox.com/security/data/fix/linux/debian-cve-2026-54875.md) | Sep 30, 2026 |
| Linux | openssl Debian 14 | 3.6.5-1 | [DEBIAN-CVE-2026-54875](https://patchblox.com/security/data/fix/linux/debian-cve-2026-54875.md) | Sep 30, 2026 |
| Linux | openssl Ubuntu 26.04.1 LTS (resolute) | 3.5.5-1ubuntu3.6 | [openssl 3.5.5-1ubuntu3.6](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-openssl-3.5.5-1ubuntu3.6.md) | Sep 28, 2026 |
| Linux | openssl-3 opensuse-leap 16.0 | 3.5.0-160000.11.1 | [OPENSUSE-SU-2026:22102-1](https://patchblox.com/security/data/fix/linux/opensuse-su-2026-22102-1.md) | Nov 7, 2026 |
| Linux | openssl-3 sles 15.7 | 3.5.0-150700.5.53.2 | [SUSE-SU-2026:4414-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-4414-1.md) | Oct 2, 2026 |
| Linux | openssl-3 sles 16.0 | 3.5.0-160000.11.1 | [SUSE-SU-2026:24245-1](https://patchblox.com/security/data/fix/linux/suse-su-2026-24245-1.md) | Nov 7, 2026 |
| Linux | openssl-provider-legacy Ubuntu 26.04.1 LTS (resolute) | 3.5.5-1ubuntu3.6 | [openssl-provider-legacy 3.5.5-1ubuntu3.6](https://patchblox.com/security/data/fix/linux/ubuntu-resolute-openssl-provider-legacy-3.5.5-1ubuntu3.6.md) | Sep 28, 2026 |

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Data as of 2026-11-08T00:53:09Z UTC. Source: Patchblox Patch Radar (https://patchblox.com/security/patch-radar). Patchblox finds out-of-date software on Windows, macOS and Linux and updates it through release rings: https://patchblox.com/demo

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