CVE-2025-40925VulnerabilityPublished 20 Sep 2025Updated 22 Sep 2025

CVE-2025-40925: BLUEFEET Starch · Generation of Predictable Numbers or Identifiers

Affects BLUEFEET StarchSource CVE Database V5

Not known to be exploited · CVSS 9.1 Critical.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

9.1Critical

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 29% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
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: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
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: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to 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 20 Sep 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 2026-10-25.

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 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.

cwe-338

What to do

Affected software

Product	Affected	Fixed in
BLUEFEET Starch	Affected =0.01	Fixed in–

AI-suggested

1. Immediate mitigation involves disabling or replacing the default session ID generator in Starch with a cryptographically secure random number generator (CSPRNG) that uses strong entropy sources, such as /dev/urandom or platform-specific secure RNG APIs. 2. If possible, upgrade to a patched version of Starch once released by BLUEFEET that addresses this vulnerability. 3. Implement additional session management controls such as session expiration, IP address binding, and multi-factor authentication to reduce the impact of session hijacking. 4. Monitor logs and network traffic for anomalous session activity indicative of session prediction or hijacking attempts. 5. Review HTTP headers to ensure sensitive timing information (e.g., Date header) is not unnecessarily exposed, reducing entropy leakage. 6. Conduct code audits and penetration testing focused on session management to identify and remediate similar weaknesses. 7. Educate developers and system administrators about secure session ID generation best practices and the risks of predictable identifiers. 8. Employ Web Application Firewalls (WAFs) with rules to detect and block suspicious session ID usage patterns.

Description

Starch versions 0.14 and earlier generate session ids insecurely. The default session id generator returns a SHA-1 hash seeded with a counter, the epoch time, the built-in rand function, the PID, and internal Perl reference addresses. The PID will come from a small set of numbers, and the epoch time may be guessed, if it is not leaked from the HTTP Date header. The built-in rand function is unsuitable for cryptographic usage. Predicable session ids could allow an attacker to gain access to systems.

Impact

For European organizations, this vulnerability poses a significant risk to web applications or services utilizing the BLUEFEET Starch framework, especially those handling sensitive or regulated data. Predictable session IDs can lead to session hijacking, allowing attackers to impersonate legitimate users, access confidential information, manipulate data, or escalate privileges. This is particularly critical for sectors such as finance, healthcare, government, and e-commerce, where data protection and privacy regulations like GDPR impose strict requirements. Unauthorized access incidents could result in data breaches, regulatory fines, reputational damage, and operational disruptions. Since the vulnerability requires no authentication or user interaction, it can be exploited remotely over the network, increasing the attack surface. The lack of known exploits currently offers a window for proactive defense, but the critical severity demands urgent attention. Organizations relying on Starch for session management must assess exposure and prioritize remediation to prevent potential compromise.

CWE-340Generation of Predictable Numbers or Identifiers (opens in a new tab)
Class weaknessOWASP Top 10 A04:2025: Cryptographic Failures (opens in a new tab)
The product uses a scheme that generates numbers or identifiers that are more predictable than required.
OWASP Cheat Sheets
Forgot Password (opens in a new tab)
Transport Layer Protection (opens in a new tab)
User Privacy Protection (opens in a new tab)
Password Storage (opens in a new tab)
Cryptographic Storage (opens in a new tab)
OWASP ASVS 4.0.3
V2.3.1 (opens in a new tab)
V2.6.2 (opens in a new tab)
V2.7.6 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 28 Sep 2025, 00:44 UTC

WeaknessesCWE-340

Technical details

References

Community reviews

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