VulnerabilityPublished 5 Mar 2026Updated 21 Apr 2026

CVE-2025-40931: CHORNY Apache::Session::Generate::MD5 · Generation of Predictable Numbers or Identifiers

Affects CHORNY Apache::Session::Generate::MD5Source CVE Database V5

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Not known to be exploited · CVSS 9.1 Critical.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

9.1Critical

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

Contested

Critical score, yet low EPSS after six months

EPSS: 0.6% chance of exploitation in 30 days – higher than 48% 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 5 Mar 2026
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 30 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.
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
CHORNYApache::Session::Generate::MD5	Affected <=1.94	Fixed in–
GitHubApache-Session`pkg:github/Apache-Session`Other threats	Affected <=1.94	Fixed in–

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

AI-suggested

As a mitigation, users of Debian-based distributions should verify if their libapache-session-perl package has been patched to use Crypt::URandom instead of the vulnerable MD5 generator. Until an official fix is available, consider replacing Apache::Session::Generate::MD5 with a cryptographically secure session ID generator.

Description

CVE-2025-40931 affects Apache::Session::Generate::MD5 for Perl, which generates session IDs using an insecure method. The session IDs are created by hashing a combination of the built-in rand() function, epoch time, and process ID (PID) with MD5. Because rand() is not cryptographically secure, and the PID and epoch time can be guessed or inferred, the session IDs are predictable. This predictability could allow attackers to hijack sessions and gain unauthorized access. Some Debian-based distributions have patched this by replacing the generator with Crypt::URandom. No official patch or vendor advisory is provided for the original module. The vulnerability has a CVSS score of 9.1, indicating critical severity.

Impact

The vulnerability allows attackers to predict session IDs due to weak randomness in the generation process. This can lead to session hijacking and unauthorized access to systems using the affected Apache::Session::Generate::MD5 module. The CVSS score of 9.1 reflects high confidentiality and integrity impact with no availability impact. There are no known exploits in the wild at this time.

Summary

Apache::Session::Generate::MD5 versions through 1.94 generate session IDs insecurely by using MD5 hashes seeded with the built-in rand() function, epoch time, and PID. The rand() function is unsuitable for cryptographic purposes, and the PID and epoch time values are predictable or guessable, leading to predictable session identifiers. This vulnerability (CVE-2025-40931) can allow attackers to predict session IDs and potentially gain unauthorized access to systems relying on these sessions. Some Debian-based Linux distributions have mitigated this issue by patching the libapache-session-perl package to use Crypt::URandom instead of the insecure generator.

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).
CWE-338Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG) (opens in a new tab)
Base weaknessLikelihood of exploit: MediumOWASP Top 10 A04:2025: Cryptographic Failures (opens in a new tab)
The product uses a Pseudo-Random Number Generator (PRNG) in a security context, but the PRNG's algorithm is not cryptographically strong.
Implementation
Use functions or hardware which use a hardware-based random number generation for all crypto. This is the recommended solution. Use CyptGenRandom on Windows, or hw_rand() on Linux.
OWASP Cheat Sheets
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)
HSTS (opens in a new tab)
OWASP ASVS 4.0.3
V6.3.3 (opens in a new tab)
V6.3.2 (opens in a new tab)
V6.3.1 (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 28 Apr 2026, 06:09 UTC

WeaknessesCWE-340, CWE-338

Technical details

References

Community reviews

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