LowCVE-2026-54875

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

Published 29.09.2026Last modified 08.10.2026Sources: Red Hat, SUSE, Ubuntu, Debian, BSI, EUVD, CVE.org, Msrc Update Guide

What is affected, what to do

A flaw was found in OpenSSL. The optimized scalar point multiplication used for SM2 cryptographic operations on ARM64 and RISC-V architectures does not execute in constant time.

Update OpenSSL to version 4.0.3, OpenSSL to version 3.6.5, OpenSSL to version 3.5.9.

Affected: OpenSSL lt 4.0.0..4.0.3
OpenSSL lt 3.6.0..3.6.5
OpenSSL lt 3.5.0..3.5.9
OpenSSL lt 3.4.0..3.4.8
Fixed in: OpenSSL 4.0.3
OpenSSL 3.6.5
OpenSSL 3.5.9
OpenSSL 3.4.8

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Metrics

3.7

XIEM Effective CVSS

Highest available CVSS rating from NVD and vendor data.

Source: Vendor (CNA), CVSS v3

3.7

CVSS v3

Severity Low on the scale from 0 to 10.

Source: Red Hat, SUSE, Ubuntu, Debian, BSI, EUVD, CVE.org, Msrc Update Guide

0.5 %

EPSS score

Low — model estimates < 1% exploitation likelihood.

Source: FIRST EPSS, percentile 41.8

Show all metrics

Severity: Low
Priority (0–325) The priority score is a consolidated metric that condenses several individual signals into a single, action-guiding ranking: technical severity (CVSS), exploitation likelihood (EPSS), known-exploited status (KEV) and the context of the affected asset. The aim is to answer the only truly important question in vulnerability management: what first? Read in glossary: 59.60 Methodology
Exploit maturity An exploit is code or a technique that specifically uses a concrete vulnerability to force unintended behaviour — such as executing code or escalating privileges. It is the tool that turns a theoretical flaw into a practical attack. Read in glossary: no public PoC known
XIEM Effective CVSS XIEM® is the tiered managed-security operating model from NEOSEC and a registered trademark of NEOSEC GmbH. It extends classic SIEM — the central collection, normalisation and correlation of security-relevant events — with endpoint forensics, network visibility and deception technology, and consolidates them into three building tiers: Sentry, Orchestrate and Command. Read in glossary: 3.7 Methodology
CVSS v3 CVSS is the globally established, open standard for assessing the technical severity of a vulnerability on a scale from 0 to 10. It describes how easily a flaw can be exploited and what damage it can cause — but not how likely its actual exploitation is. CVSS and the complementary EPSS deliberately answer different questions. Read in glossary: 3.7
EPSS score The EPSS score is the absolute model output for an individual vulnerability: the estimated probability of real-world exploitation within the next 30 days, expressed as a value between 0 and 1 (i.e. 0 % to 100 %). A score of 0.42 means „the model estimates a 42 % chance of real-world exploitation within 30 days“. Read in glossary: 0.5 %; Low — model estimates < 1% exploitation likelihood.
EPSS percentile The EPSS percentile is the relative position of a vulnerability within all EPSS-scored CVEs, expressed as a value between 0 and 1. A percentile of 0.90 means „this CVE has a higher EPSS score than 90 % of all other scored CVEs“. Unlike the EPSS score, it is not a probability — but a positioning within a ranking. Read in glossary: 41.8; High — this CVE ranks above the median of all CVEs scored today (rank ≥ 36%).
KEV status The KEV catalogue is a list maintained by the US authority CISA of vulnerabilities for which active exploitation in the wild has been confirmed. It answers not the question „how severe?“ but „is it already being attacked?“ — thereby sharply prioritising patching. Read in glossary: —
Published: 29.09.2026
CISA assessment (SSVC): Exploitation: none known · not automatable · Technical impact: partial; Source: CISA Vulnrichment, as of 29 September 2026
CWE CWE is a catalogue of typical weakness types in software and hardware — such as flawed input validation, unsafe memory handling or poor authentication. Where a CVE names a concrete vulnerability in a concrete product, a CWE describes the underlying class of defect. Read in glossary: CWE-208

Detection rules

No NEOSEC detection rule is available for this vulnerability yet.

Classification under NIS2 and CRA

Rule-based classification from exploitation status and severity. It does not replace a case-by-case assessment.

NIS2 NIS2 is EU Directive (EU) 2022/2555 to raise the level of cybersecurity across the Union. It substantially broadens obligations compared with the first NIS directive: more sectors, mandatory risk management, staged reporting duties and personal accountability of senior management. Read in glossary: Handle the vulnerability in regular vulnerability handling under Art. 21(2)(e) NIS2.
CRA The CRA is EU Regulation (EU) 2024/2847 setting horizontal cybersecurity requirements for „products with digital elements“ — from industrial controllers and software to connected consumer devices. For the first time manufacturers must ensure security across the entire product lifecycle, handle vulnerabilities and provide security updates. Read in glossary: From 11.12.2027, Annex I Part II CRA requires manufacturers of affected products with digital elements to handle vulnerabilities without delay and provide security updates.
ISO/IEC 27001 ISO/IEC 27001 is the internationally leading standard for an information security management system (ISMS). It describes a risk-based, process-oriented framework to systematically plan, implement, review and improve information security. Read in glossary: Control A.8.8, management of technical vulnerabilities: assess relevance to your systems, plan remediation and keep evidence.

Description

A flaw was found in OpenSSL. The optimized scalar point multiplication used for SM2 cryptographic operations on ARM64 and RISC-V architectures does not execute in constant time. An attacker capable of measuring execution times or observing processor cache-access patterns can exploit this side channel during decryption or digital signature generation. This vulnerability allows the attacker to deduce sensitive private keys or signature nonces, leading to information disclosure.

Source: redhat_csaf, suse_csaf, Ubuntu Security Notices, Debian Security Advisories, BSI WID Portal, BSI CSAF, ENISA EUVD, NVD (NIST), cvelistv5, Microsoft Security Update Guide

Affected products

The following versions are affected. Older releases of the same product line are also vulnerable unless stated otherwise.

Affected products
		Affected versions	Fixed in
OpenSSL	OpenSSL	`3.4.0 – < 3.4.8` `3.5.0 – < 3.5.9` `3.6.0 – < 3.6.5` `4.0.0 – < 4.0.3`	`3.4.8` `3.5.9` `3.6.5` `4.0.3`
openssl	openssl	`4.0.0 – < 4.0.3` `3.5.0 – < 3.5.9` `3.6.0 – < 3.6.5` `3.4.0 – < 3.4.8`	`4.0.3` `3.5.9` `3.6.5` `3.4.8`

Vendors and products

Affected operating systems

Affected operating systems

Linux	debian	openssl	`trixie`

Weakness classes (CWE)

CWE-208Observable Timing Discrepancy
Base
Two separate operations in a product require different amounts of time to complete, in a way that is observable to an actor and reveals security-relevant information about the state of the product, such as whether a particular operation was successful or not.
Entry at MITRE CWE-208

References & sources

openssl-library.orgOpenSSL AdvisoryVendor advisory, euvd
github.com4.0.3 git commitPatch, euvd
github.com3.6.5 git commitPatch, euvd
github.com3.5.9 git commitPatch, euvd
github.com3.4.8 git commitPatch, euvd

Changes to this CVE

Who changed this CVE and when: NVD (analysis, affected products, CVSS), the CVE publisher (CNA) and additional providers such as CISA (ADP).

08.10.2026Initial analysis by NVDNVD

Newly listed as affected:

OpenSSL (3.4.0 – before 3.4.8; 3.5.0 – before 3.5.9; 3.6.0 – before 3.6.5; 4.0.0 – before 4.0.3)

New references:

and 1 more reference

Show 6 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Product configuration	added	—	OR cpe:2.3:a:openssl:openssl::::::::* versions from (including) 3.4.0 up to (excluding) 3.4.8 cpe:2.3:a:openssl:openssl::::::::* versions from (including) 3.5.0 up to (excluding) 3.5.9 cpe:2.3:a:openssl:openssl::::::::* versions from (including) 3.6.0 up to (excluding) 3.6.5 cpe:2.3:a:openssl:openssl::::::::* versions from (including) 4.0.0 up to (excluding) 4.0.3
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/3f01bbc28f7e08211fcdc797fd43816504f94257 Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/469f3e42629f4a0b5631796e20c66c92c138a3e8 Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/9794ed473764839275cb701b4850f3c24d929c28 Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/dddad955d5ff3e9507619cf4e0f13e9988e2197c Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://openssl-library.org/news/secadv/20260929.txt Types: Vendor Advisory

Source identifier: nvd@nist.gov

29.09.2026Record modifiedCISA ADP

CVSS V3.1: AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

CISA assessment (SSVC): exploitation: none known, automatable: no

Show 2 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
CVSS	added	—	AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N
SSVC assessment	added	—	{"id":"CVE-2026-54875","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-09-29T17:17:05.164162Z"}

Source identifier: 134c704f-9b21-4f2e-91b3-4a467353bcc0

29.09.2026Receivedopenssl.org

Weakness type: CWE-208

Description added or changed

New references:

and 1 more reference

Show 8 original changes

Individual changes of this event as published by NVD
Type	Action	Before	After
Description	added	—	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
Weakness type (CWE)	added	—	CWE-208
Affected versions (publisher)	added	—	New affected value received. <a href="https://github.com/CVEProject/cvelistV5/blob/main/cves/2026/54xxx/CVE-2026-54875.json">CVE-2026-54875</a>
Reference	added	—	https://github.com/openssl/openssl/commit/3f01bbc28f7e08211fcdc797fd43816504f94257
Reference	added	—	https://github.com/openssl/openssl/commit/469f3e42629f4a0b5631796e20c66c92c138a3e8
Reference	added	—	https://github.com/openssl/openssl/commit/9794ed473764839275cb701b4850f3c24d929c28
Reference	added	—	https://github.com/openssl/openssl/commit/dddad955d5ff3e9507619cf4e0f13e9988e2197c
Reference	added	—	https://openssl-library.org/news/secadv/20260929.txt

Source identifier: openssl-security@openssl.org

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