CVE-2025-57784: 
NixOS vulnerability analysis and mitigation

CVE-2025-57784 is a timing side-channel vulnerability in the Tomahawk management client authentication of the Hiawatha web server, caused by the use of the non-constant-time strcmp function for password comparison. This flaw allows a local attacker with low privileges to potentially bypass authentication and gain access to the Hiawatha management client. The vulnerability affects Hiawatha version 11.7 (and reportedly versions ≤ 8.5 per ENISA). It was published on January 26, 2026, and carries a CVSS v3.1 base score of 3.3 (Low) per NVD, or 4.0 per ENISA (CERT Advisory, Red Hat CVE).

The root cause is classified as CWE-208 (Observable Timing Discrepancy). The vulnerable code resides in src/tomahawk.c at approximately line 429, where the standard C strcmp function is used to compare authentication passwords (CERT Advisory). Because strcmp returns early upon finding the first differing character, the time taken to complete the comparison varies depending on how many leading characters of the submitted password match the correct one. A local attacker can exploit this by submitting many password guesses and measuring response times to statistically infer the correct password character by character. Exploitation requires local access and low privileges, with no user interaction needed.

Successful exploitation allows a local attacker to deduce the Tomahawk management client password through timing analysis, ultimately gaining unauthorized access to the Hiawatha web server's management interface. The confidentiality impact is limited — an attacker can read management client credentials or configuration — while integrity and availability are not directly affected by this vulnerability. The scope is constrained to the local system and the management interface, limiting lateral movement potential (CERT Advisory, Red Hat CVE).

No public exploit code or active in-the-wild exploitation has been reported for CVE-2025-57784. The EPSS score is approximately 0.012% (0.000120), indicating a very low probability of exploitation in the near term. The vulnerability is not listed in the CISA Known Exploited Vulnerabilities (KEV) catalog. Exploitation requires local access, making it a lower-priority risk compared to remotely exploitable vulnerabilities (CERT Advisory).

1. Gain local access: Obtain a low-privileged local account on the system running Hiawatha 11.7 with Tomahawk management enabled.
2. Identify the Tomahawk socket/port: Locate the Tomahawk management client interface (typically a local Unix socket or TCP port as configured in hiawatha.conf).
3. Craft timing attack: Write or use a timing-based script that submits authentication attempts to the Tomahawk interface, varying the password one character at a time and measuring the response time for each attempt.
4. Statistical analysis: Collect a large number of timing samples per candidate character to reduce noise; characters that cause longer response times indicate a match at that position (due to strcmp comparing more characters before returning).
5. Reconstruct password: Repeat the process for each character position until the full password is recovered, then authenticate to the Tomahawk management client with the discovered credentials (CERT Advisory, Security Online).

• Logs: Unusually high volume of failed or repeated authentication attempts against the Tomahawk management interface in Hiawatha logs.
• Process/Network: Unexpected local processes making rapid, repeated connections to the Tomahawk management socket or port.
• Behavioral: Successful Tomahawk management logins from unexpected local user accounts or at unusual times.

Users should upgrade Hiawatha to a version that replaces the strcmp call in tomahawk.c with a constant-time string comparison function (e.g., timingsafe_bcmp or equivalent). As a workaround, restrict access to the Tomahawk management interface to only trusted users via OS-level permissions, and consider disabling the Tomahawk management client if it is not required. Monitor the Hiawatha project's GitLab repository for patched releases (CERT Advisory, Hiawatha Source).

The vulnerability was covered briefly by Security Online, which noted it alongside other Hiawatha web server flaws including authentication bypass and RCE issues (Security Online). It was also referenced in The Hacker News' weekly recap covering zero-days and supply chain issues, though without dedicated analysis (The Hacker News). Community reaction has been minimal given the low CVSS score and local-only attack vector.