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

2026-09-30T10:21:38.639747+00:00

Affected: OpenSSL

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.

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USN-8847-1 — openssl vulnerabilities

2026-09-30T10:21:38.639923+00:00

Affected: Ubuntu:22.04:LTS: openssl, Ubuntu:24.04:LTS: openssl, Ubuntu:26.04:LTS: openssl

It was discovered that OpenSSL incorrectly handled certain certificate revocation list distribution point names. An attacker could possibly use this issue to cause OpenSSL to consume excessive memory, resulting in a denial of service. (CVE-2026-35189)

It was discovered that OpenSSL incorrectly handled QUIC unvalidated amplification credit accounting. An attacker could possibly use this issue to cause a denial of service. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-35191)

It was discovered that OpenSSL incorrectly implemented scalar multiplication for non-NIST elliptic curves. An attacker could possibly use this issue to perform a timing side-channel attack and obtain sensitive information. (CVE-2026-54872)

It was discovered that OpenSSL incorrectly implemented SM2 scalar multiplication on ARM64 and RISC-V architectures. An attacker could possibly use this issue to perform a timing side-channel attack and obtain sensitive information. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-54875)

It was discovered that OpenSSL incorrectly handled SSL context switching during a TLS handshake. An attacker could possibly use this issue to cause an out-of-bounds read, resulting in a denial of service or obtaining sensitive information. This issue only affected Ubuntu 26.04 LTS. (CVE-2026-72897)

It was discovered that OpenSSL incorrectly enforced QUIC connection- level flow control for streams. An attacker could possibly use this issue to cause OpenSSL to consume excess…