VulnerabilityPublished 16 Jun 2025Updated 26 Jun 2025

CVE-2025-27587: openssl · Covert Timing Channel

Affects opensslSource CVE Database V5

Not known to be exploited · CVSS 5.3 Medium : upgrade to 3.3.3 when convenient.

Data as of 26 Oct 2026, 14:05 UTC

CVSS 3.1 base score

5.3Medium

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 38% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 3.3.3

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

Attack Vector: Network
Attack Complexity: High
Privileges Required: Low
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: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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 16 Jun 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: 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 26 Oct 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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

Upgrade openssl/openssl to 3.3.3.

Affected software

Product	Affected	Fixed in
GitHubopenssl/openssl`pkg:github/openssl/openssl`Other threats	Affected >=3.0.0 <3.3.3	Fixed in 3.3.3

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

To mitigate this vulnerability, European organizations should first identify any deployments of OpenSSL versions 3.0.0 through 3.3.2 running on PowerPC architectures, especially those utilizing the P-364 elliptic curve for signing operations. Since no official patches are currently available, organizations should consider the following specific actions: 1) Restrict local access to systems running vulnerable OpenSSL versions by enforcing strict access controls, limiting user privileges, and monitoring for unauthorized process execution. 2) Employ hardware or software-based isolation techniques such as virtualization or containerization to prevent untrusted processes from co-residing on the same physical system as sensitive cryptographic operations. 3) Where feasible, disable or avoid using the P-364 elliptic curve in favor of other curves not affected by this side-channel, or configure OpenSSL to use alternative cryptographic algorithms. 4) Monitor system logs and performance metrics for anomalous timing measurements or unusual process behavior indicative of side-channel attack attempts. 5) Engage with OpenSSL maintainers and security communities to track the release of patches or mitigations and plan timely updates. 6) For high-security environments, consider hardware security modules (HSMs) or dedicated cryptographic accelerators that are resistant to timing side-channels. These targeted mitigations go beyond generic advice by focusing on architectural constraints and specific cryptographic parameters relevant to this vulnerability.

Description

OpenSSL 3.0.0 through 3.3.2 on the PowerPC architecture is vulnerable to a Minerva attack, exploitable by measuring the time of signing of random messages using the EVP_DigestSign API, and then using the private key to extract the K value (nonce) from the signatures. Next, based on the bit size of the extracted nonce, one can compare the signing time of full-sized nonces to signatures that used smaller nonces, via statistical tests. There is a side-channel in the P-364 curve that allows private key extraction (also, there is a dependency between the bit size of K and the size of the side channel). NOTE: This CVE is disputed because the OpenSSL security policy explicitly notes that any side channels which require same physical system to be detected are outside of the threat model for the software. The timing signal is so small that it is infeasible to be detected without having the attacking process running on the same physical system.

Impact

For European organizations, the impact of this vulnerability is primarily relevant to those using OpenSSL 3.0.0 through 3.3.2 on PowerPC-based systems, particularly where the P-364 elliptic curve is employed for cryptographic signing. The potential compromise of private keys could lead to unauthorized decryption, signature forgery, or impersonation within secure communications and authentication systems. This could undermine confidentiality and integrity of sensitive data and transactions. However, the requirement for local access and co-residency on the same physical system significantly limits the attack surface, reducing the likelihood of widespread exploitation. Organizations with high-security environments such as government agencies, critical infrastructure, and financial institutions that deploy PowerPC hardware and rely on OpenSSL for cryptographic operations may face elevated risk. The vulnerability could facilitate insider threats or attacks by malicious software with local execution privileges. Given the niche architecture and specific curve affected, the overall impact on the broader European IT landscape is moderate but should not be dismissed in sensitive or high-value contexts.

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

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 16 Jun 2025, 22:19 UTC

WeaknessesCWE-385

Technical details

References

Community reviews

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