LowCVE-2026-54872

Timing Side-Channel in Scalar Multiplication for Non-NIST EC Curves (CVE-2026-54872)

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

What is affected, what to do

A flaw was found in OpenSSL. A timing side-channel vulnerability in generic elliptic curve scalar multiplication allows an attacker to recover private cryptographic keys.

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
OpenSSL lt 3.0.0..3.0.23
OpenSSL lt 1.1.1..1.1.1zj
OpenSSL lt 1.0.2..1.0.2zs
Fixed in: OpenSSL 4.0.3
OpenSSL 3.6.5
OpenSSL 3.5.9
OpenSSL 3.4.8
OpenSSL 3.0.23
OpenSSL 1.1.1zj
OpenSSL 1.0.2zs

Not sure whether and how you are affected? Ask a question about this vulnerability

Metrics

3.7

Priority

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

0.4 %

EPSS score

Low — model estimates < 1% exploitation likelihood.

Source: FIRST EPSS, percentile 37.0

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: 59.39 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: 0.4 %; 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: 37.0; 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. A timing side-channel vulnerability in generic elliptic curve scalar multiplication allows an attacker to recover private cryptographic keys. When performing signature operations, such as the Elliptic Curve Digital Signature Algorithm (ECDSA) or SM2, using curves without dedicated constant-time implementations, variations in processing time leak information about the per-signature secret value. By measuring the duration of numerous signing operations, an attacker can analyze these timing differences to reconstruct the private signing key.

Source: Ubuntu Security Notices, suse_csaf, Debian LTS Advisories, redhat_csaf, Debian Security Advisories, BSI WID Portal, BSI CSAF, 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` `1.0.2 – < 1.0.2zs` `1.1.1 – < 1.1.1zj` `3.0.0 – < 3.0.23` `4.0.0 – < 4.0.3`	`3.4.8` `3.5.9` `3.6.5` `1.0.2zs` `1.1.1zj` `3.0.23` `4.0.3`
openssl	openssl	`4.0.0 – < 4.0.3` `3.5.0 – < 3.5.9` `3.0.0 – < 3.0.23` `1.0.2 – < 1.0.2zs` `3.6.0 – < 3.6.5` `3.4.0 – < 3.4.8` `1.1.1 – < 1.1.1zj`	`4.0.3` `3.5.9` `3.0.23` `1.0.2zs` `3.6.5` `3.4.8` `1.1.1zj`
Open Source	OpenSSL	`< 1.1.1zj` `< 1.0.2zs` `< 3.4.8` `< 3.6.5` `< 3.5.9` `< 3.0.23` `< 4.0.3`	`1.1.1zj` `1.0.2zs` `3.4.8` `3.6.5` `3.5.9` `3.0.23` `4.0.3`

Vendors and products

Affected operating systems

Affected operating systems

Linux	debian	openssl	`bookworm`
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
github.com4.0.3 git commitPatch
github.com3.6.5 git commitPatch
github.com3.5.9 git commitPatch
github.com3.4.8 git commitPatch

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; 1.0.2 – before 1.0.2zs; 1.1.1 – before 1.1.1zj; 3.0.0 – before 3.0.23)

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 cpe:2.3:a:openssl:openssl::::::::* versions from (including) 1.0.2 up to (excluding) 1.0.2zs cpe:2.3:a:openssl:openssl::::::::* versions from (including) 1.1.1 up to (excluding) 1.1.1zj cpe:2.3:a:openssl:openssl::::::::* versions from (including) 3.0.0 up to (excluding) 3.0.23
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/1a5bee8dc57430a2be69cd1ffe7fec6a62f4f179 Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/3f7e1363dccec6f7732bb9e9fa471bb6e4aa68cb Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/7d83bc7764999dfd91b83b4f0815b45390422afd Types: Patch
Reference type	added	—	OpenSSL Software Foundation: https://github.com/openssl/openssl/commit/8166827a78aad164a07aa86dea2b425403ced471 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-2026-54872","role":"CISA Coordinator","options":[{"exploitation":"none"},{"automatable":"no"},{"technicalImpact":"partial"}],"version":"2.0.3","timestamp":"2026-09-29T17:27:46.959054Z"}

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: The generic elliptic-curve scalar multiplication used for ECDSA and SM2 signature operations with curves that do not have a dedicated implementation leaks information about the secret nonce through timing. Impact summary: An attacker able to measure signing times may learn information about the per-signature secret nonce, which over many signatures can, via a lattice / Hidden Number Problem attack, lead to recovery of the private key. CWE: CWE-208: Observable Timing Discrepancy Description: The generic elliptic-curve scalar multiplication used for curves that do not have a dedicated constant-time implementation pads the secret scalar with non-constant-time BIGNUM operations, so the time taken depends on the value of the secret scalar derived from the ECDSA and SM2 nonce. The leak is very small; observing it requires a large number of measurements. The effect is largest for curves whose group order lies on a machine-word boundary, such as brainpoolP384r1. Applications using ECDSA signing over the Brainpool and other generic prime curves, and SM2 signing on platforms that use the generic implementation, are vulnerable to this issue. The NIST curves P-256, P-384 and P-521 use dedicated constant-time implementations and are not affected. FIPS Impact: no The FIPS modules are not affected: the approved NIST curves used in the FIPS provider have dedicated constant-time implementations and do not use the affected code path.
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-2026-54872.json">CVE-2026-54872</a>
Reference	added	—	https://github.com/openssl/openssl/commit/1a5bee8dc57430a2be69cd1ffe7fec6a62f4f179
Reference	added	—	https://github.com/openssl/openssl/commit/3f7e1363dccec6f7732bb9e9fa471bb6e4aa68cb
Reference	added	—	https://github.com/openssl/openssl/commit/7d83bc7764999dfd91b83b4f0815b45390422afd
Reference	added	—	https://github.com/openssl/openssl/commit/8166827a78aad164a07aa86dea2b425403ced471
Reference	added	—	https://openssl-library.org/news/secadv/20260929.txt

Source identifier: openssl-security@openssl.org

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