VulnerabilityPublished 8 Apr 2026

CVE-2026-5082: TOKUHIROM Amon2::Plugin::Web::CSRFDefender · Generation of Predictable Numbers or Identifiers

Affects TOKUHIROM Amon2::Plugin::Web::CSRFDefenderSource CVE Database V5

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Mentioned vulnerabilities

CVE-2025-15604

Not known to be exploited · CVSS 5.3 Medium.

Data as of 29 Oct 2026, 19:04 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 34% 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:N/I:N/A:L

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

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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 8 Apr 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 29 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
TOKUHIROMAmon2::Plugin::Web::CSRFDefender	Affected >=7.00 <=7.03	Fixed in–
GitHubAmon2-Plugin-Web-CSRFDefender`pkg:github/Amon2-Plugin-Web-CSRFDefender`Other threats	Affected >=7.00 <=7.03	Fixed in–

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

AI-suggested

Since the module is deprecated, users should consider migrating to alternative, actively maintained CSRF defense solutions that use secure random number generation. Avoid relying on this module for session ID generation, especially in environments where /dev/urandom might be unavailable. Monitor vendor advisories for any future updates or recommendations.

Description

CVE-2026-5082 affects Amon2::Plugin::Web::CSRFDefender versions 7.00 through 7.03 for Perl, where the module generates insecure session IDs. The vulnerability arises because if /dev/urandom is unavailable, the session ID generation falls back to a SHA-1 hash seeded with the built-in rand() function, process ID, and epoch time, which are predictable or guessable values. This weak randomness can lead to predictable session identifiers. The module has been deprecated by its author. No official patch or remediation is currently documented.

Impact

The vulnerability allows attackers to predict session IDs generated by the affected module under certain conditions, potentially undermining session integrity. However, the CVSS score of 5.3 (medium severity) and vector indicate no confidentiality or integrity impact, only a potential availability impact. There are no known exploits in the wild. The module's deprecation suggests it may no longer be maintained or recommended for use.

Summary

Amon2::Plugin::Web::CSRFDefender versions 7.00 through 7.03 generate session IDs insecurely when /dev/urandom is not accessible. The fallback method uses a SHA-1 hash seeded with the built-in rand() function, process ID (PID), and high-resolution epoch time. Since the PID is from a small range and the epoch time may be inferred (e.g., from HTTP Date headers), the session IDs can be predicted. The built-in rand() function is not cryptographically secure, making the session ID generation vulnerable to prediction. Earlier versions before 7.00 were also vulnerable due to a related issue (CVE-2025-15604).

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 15 Apr 2026, 15:53 UTC

WeaknessesCWE-340, CWE-338

Technical details

References

Community reviews

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