VulnerabilityPublished 30 Sep 2025Updated 6 Nov 2026

CVE-2025-9231: OpenSSL · Covert Timing Channel

Affects OpenSSLSource GCVE Database

Compare

Not known to be exploited · CVSS 5.9 Medium.

Data as of 6 Nov 2026, 23:24 UTC

CVSS 3.1 base score

5.9Medium

How severe the flaw is on the 0–10 CVSS scale.

Thin evidence

One scorer or none

CVSS scores by source
CISA-ADP	CVSS 3.1	5.9

EPSS: 2.2% chance of exploitation in 30 days – higher than 82% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: None
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 30 Sep 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 6 Nov 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
OpenSSL OpenSSL	Affected 3.2.0 – 3.5.0 3.5.0 3.4.0 3.3.0 3.2.0 4 affected builds	Fixed in–

AI-suggested

Users should avoid deploying SM2 algorithm implementations on 64-bit ARM platforms within the affected OpenSSL versions. Since OpenSSL does not natively support SM2 certificates in TLS, avoiding custom providers that add such support mitigates risk. Monitoring vendor advisories for updates or patches is recommended. The FIPS modules are not affected and can be used as a secure alternative where applicable.

Description

CVE-2025-9231 is a timing side-channel vulnerability in the SM2 algorithm implementation on 64-bit ARM platforms in OpenSSL versions 3.2.0, 3.3.0, 3.4.0, and 3.5.0. This flaw could potentially allow an attacker to recover the private key by analyzing timing variations during signature computations. The vulnerability is considered moderate severity and does not affect OpenSSL's FIPS modules or typical TLS usage since SM2 certificates are not directly supported in TLS by default. Exploitation over a network has not been demonstrated but remains a theoretical risk if custom providers add SM2 support.

Impact

An attacker with the ability to measure timing variations in SM2 signature computations on 64-bit ARM platforms could potentially recover the private key. This could compromise the confidentiality of cryptographic keys used in affected OpenSSL versions. However, since OpenSSL does not directly support SM2 certificates in TLS, the practical impact is limited unless custom providers enable SM2 support. The FIPS modules are unaffected, reducing risk in FIPS-compliant environments.

Summary

This vulnerability (CVE-2025-9231) involves a covert timing channel in the SM2 signature algorithm implementation on 64-bit ARM architectures within OpenSSL versions 3.2.0 through 3.5.0. The timing side-channel could leak information about the private key during signature operations. Although OpenSSL does not natively support SM2 certificates in TLS, custom providers can add such support, potentially exposing private keys to remote timing attacks. The FIPS modules for OpenSSL versions 3.0 through 3.5 are not affected because SM2 is not an approved algorithm in those modules. The CVSS v3.1 score is 6.5, reflecting a medium severity with network attack vector, low complexity, no privileges or user interaction required, and limited confidentiality impact.

CWE-385Covert Timing Channel (opens in a new tab)
Base weaknessLikelihood of exploit: Medium
Covert timing channels convey information by modulating some aspect of system behavior over time, so that the program receiving the information can observe system behavior and infer protected information.
Architecture and Design
Whenever possible, specify implementation strategies that do not introduce time variances in operations.
Implementation
Often one can artificially manipulate the time which operations take or -- when operations occur -- can remove information from the attacker.
Implementation
It is reasonable to add artificial or random delays so that the amount of CPU time consumed is independent of the action being taken by the application.
OWASP Cheat Sheets
Cryptographic Storage (opens in a new tab)
Key Management (opens in a new tab)
OWASP ASVS 4.0.3
V6.2.8 (opens in a new tab)
Attack patterns
Cross-Domain Search Timing (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 6 Nov 2026, 20:51 UTC

WeaknessesCWE-385

Technical details

References

Community reviews

Related threats