Amon2 versions before 6.17 for Perl use an insecure random_string implementation for security functions. In versions 6.06 through 6.16, the random_string function will attempt to read bytes from the /dev/urandom device, but if that is unavailable then it generates bytes by concatenating a SHA-1 hash seeded with the built-in rand() function, the PID, and the high resolution epoch time. 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. Before version 6.06, there was no fallback when /dev/urandom was not available. Before version 6.04, the random_string function used the built-in rand() function to generate a mixed-case alphanumeric string. This function may be used for generating session ids, generating secrets for signing or encrypting cookie session data and generating tokens used for Cross Site Request Forgery (CSRF) protection.
Conclusion & alert: CVE-2025-15604 is rated Moderate Risk (41.2/100): CVSS Critical severity, with low exploitation likelihood (EPSS 0.02%). Mandatory action: Review affected assets and schedule remediation.
Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.
EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).
| # | Date | Old EPSS score | New EPSS score | Delta (New - Old) |
|---|---|---|---|---|
| 1 | 2026-04-21 | 0.06% | 0.02% | -0.04% |
| 2 | 2026-04-03 | 0.02% | 0.06% | +0.04% |
| 3 | 2026-03-29 | — | 0.02% | — |
Full EPSS history (3 records total)
CVSS metrics for this CVE.
| Base score | Version | Severity | Vector | Exploitability | Impact | Score source |
|---|---|---|---|---|---|---|
| 9.8 | 3.1 | CRITICAL |
|
3.9 | 5.9 | [email protected] |
| 9.8 | 3.1 | CRITICAL |
|
3.9 | 5.9 | 134c704f-9b21-4f2e-91b3-4a467353bcc0 |
| URL | Tags |
|---|---|
| https://github.com/tokuhirom/Amon/pull/135 | Issue Tracking Patch |
| https://metacpan.org/release/TOKUHIROM/Amon2-6.17/changes | Product |
| https://metacpan.org/release/TOKUHIROM/Amon2-6.17/diff/TOKUHIROM/Amon2-6.16#lib/Amon2/Util.pm | Product |
| https://security.metacpan.org/docs/guides/random-data-for-security.html | Third Party Advisory |
| http://www.openwall.com/lists/oss-security/2026/03/28/4 | Mailing List Third Party Advisory |