SM2 timing sidechannel in OpenSSL on 64bit ARM Enables Remote Key Recovery
CVE-2025-9231 Published on September 30, 2025
Timing side-channel in SM2 algorithm on 64 bit ARM
Issue summary: A timing side-channel which could potentially allow remote
recovery of the private key exists in the SM2 algorithm implementation on 64 bit
ARM platforms.
Impact summary: A timing side-channel in SM2 signature computations on 64 bit
ARM platforms could allow recovering the private key by an attacker..
While remote key recovery over a network was not attempted by the reporter,
timing measurements revealed a timing signal which may allow such an attack.
OpenSSL does not directly support certificates with SM2 keys in TLS, and so
this CVE is not relevant in most TLS contexts. However, given that it is
possible to add support for such certificates via a custom provider, coupled
with the fact that in such a custom provider context the private key may be
recoverable via remote timing measurements, we consider this to be a Moderate
severity issue.
The FIPS modules in 3.5, 3.4, 3.3, 3.2, 3.1 and 3.0 are not affected by this
issue, as SM2 is not an approved algorithm.
Vulnerability Analysis
CVE-2025-9231 can be exploited with network access, and does not require authorization privileges or user interaction. This vulnerability is considered to have a low attack complexity. The potential impact of an exploit of this vulnerability is considered to have a small impact on confidentiality, a small impact on integrity, and a small impact on availability.
Weakness Type
Covert Timing Channel
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.
Products Associated with CVE-2025-9231
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Affected Versions
OpenSSL:- Version 3.5.0 and below 3.5.4 is affected.
- Version 3.4.0 and below 3.4.3 is affected.
- Version 3.3.0 and below 3.3.5 is affected.
- Version 3.2.0 and below 3.2.6 is affected.
Exploit Probability
EPSS (Exploit Prediction Scoring System) scores estimate the probability that a vulnerability will be exploited in the wild within the next 30 days. The percentile shows you how this score compares to all other vulnerabilities.