CVE-2025-15604Network attack vectorHinoki check available

Token prediction via weak random_string generation

Published Mar 28, 2026 · Updated Mar 28, 2026

Predictable token generation in Tokuhiro Matsuno Amon2 before 6.17 allows remote attackers to predict session and CSRF tokens. Amon2::Util::random_string uses rand() directly before 6.04; versions 6.04 and 6.05 rely solely on /dev/urandom, while 6.06 through 6.16 fall back to SHA-1 output seeded with rand(), the PID, and guessable time. Exposure depends on applications using the function for session IDs, cookie secrets, or CSRF tokens; successful prediction permits token forgery or session compromise.

CVSS severity9.8
Critical
EPSS probability0.52%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkAvailable
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Summary

What happened

Predictable token generation in Tokuhiro Matsuno Amon2 before 6.17 allows remote attackers to predict session and CSRF tokens. Amon2::Util::random_string uses rand() directly before 6.04; versions 6.04 and 6.05 rely solely on /dev/urandom, while 6.06 through 6.16 fall back to SHA-1 output seeded with rand(), the PID, and guessable time. Exposure depends on applications using the function for session IDs, cookie secrets, or CSRF tokens; successful prediction permits token forgery or session compromise.

The record

CVE
CVE-2025-15604
Published
Mar 28, 2026
Updated
Mar 28, 2026
Vendor
Tokuhiro Matsuno
Product
Amon2
Classifications
CWE-340, CWE-338, T1550.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 28, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 28, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0 <6.17

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Tokuhiro Matsuno · Amon2version=0 <6.17

Published CVSS scores

9.8CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
9.8NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 9, 2026Sep 15, 2026
Latest reporting daySep 15, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitUnconfirmed

Weakness, pattern, technique

CWE-340Generation of Predictable Numbers or Identifiers
CWE-338Use of Cryptographically Weak Pseudo-Random Number Generator (PRNG)
T1550.004Web Session Cookie

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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