CVE-2025-57784: Hiawatha Webserver Auth Bypass Flaw

CVE-2025-57784 Overview

A timing attack vulnerability has been identified in the Tomahawk management interface of Hiawatha webserver version 11.7. The vulnerability stems from the use of strcmp for authentication comparison, which allows a local attacker to perform a timing-based attack to determine valid authentication credentials and gain unauthorized access to the management client.

Critical Impact

Local attackers can exploit timing differences in authentication responses to deduce valid credentials and access the Hiawatha webserver management interface.

Affected Products

• Hiawatha webserver version 11.7
• Tomahawk management interface

Discovery Timeline

• 2026-01-26 - CVE CVE-2025-57784 published to NVD
• 2026-01-27 - Last updated in NVD database

Technical Details for CVE-2025-57784

Vulnerability Analysis

This vulnerability is a classic timing attack against authentication mechanisms. The Tomahawk component of Hiawatha webserver uses the standard C library function strcmp to compare user-supplied credentials against stored authentication values. The strcmp function performs byte-by-byte comparison and returns immediately upon finding the first mismatched character. This behavior creates measurable timing differences that correlate with how many characters of the input match the actual credential.

An attacker with local access can repeatedly attempt authentication while precisely measuring response times. By analyzing these timing variations, the attacker can iteratively determine each character of valid credentials—effectively performing a side-channel attack that bypasses the need to know the password outright.

Root Cause

The root cause is the use of a non-constant-time string comparison function (strcmp) in the authentication routine within tomahawk.c. The vulnerable code can be reviewed at GitLab Code Review. Secure authentication implementations should use constant-time comparison functions that take the same amount of time regardless of where a mismatch occurs, preventing timing-based information leakage.

Attack Vector

The attack requires local access to the system running Hiawatha webserver. The attacker must be able to:

1. Send authentication requests to the Tomahawk management interface
2. Measure response times with sufficient precision (typically microsecond-level accuracy)
3. Perform statistical analysis across multiple authentication attempts to distinguish timing differences caused by correct versus incorrect character matches

The vulnerability mechanism works by exploiting the early-exit behavior of strcmp. When comparing two strings, if the first character differs, the function returns almost immediately. If the first character matches but the second differs, it takes slightly longer. This pattern continues for each character position, creating a timing oracle that reveals credential information.

Detection Methods for CVE-2025-57784

Indicators of Compromise

• Unusual volume of failed authentication attempts to the Tomahawk management interface from local processes
• Rapid succession of authentication requests with minimal time between attempts
• Pattern of authentication attempts showing systematic variation in input values
• Local processes repeatedly accessing the Tomahawk authentication endpoint

Detection Strategies

• Monitor authentication logs for high-frequency failed login attempts originating from local addresses
• Implement rate limiting detection to identify automated credential probing attempts
• Analyze timing patterns in authentication request sequences for statistical anomalies
• Deploy process monitoring to detect local applications attempting to interact with Tomahawk

Monitoring Recommendations

• Enable detailed logging for all Tomahawk management interface authentication events
• Configure alerting thresholds for authentication failure rates from local sources
• Implement audit logging for process-level access to Hiawatha configuration and management ports
• Review system logs regularly for signs of automated authentication probing

How to Mitigate CVE-2025-57784

Immediate Actions Required

• Restrict local access to the Tomahawk management interface to trusted administrators only
• Consider disabling the Tomahawk management interface if not actively required
• Implement additional authentication layers such as IP-based access controls
• Monitor for and investigate any suspicious authentication patterns

Patch Information

Check the Hiawatha GitLab repository for updates that replace strcmp with a constant-time comparison function. The proper fix involves using functions like CRYPTO_memcmp from OpenSSL or implementing a custom constant-time comparison that evaluates all bytes regardless of mismatches.

Workarounds

• Disable the Tomahawk management interface entirely if administrative access is not required
• Restrict management interface access to specific trusted local users using file system permissions
• Implement network-level controls to limit connections to the management port
• Use strong, randomly-generated credentials to increase the time required for successful timing attacks

# Example: Disable Tomahawk in Hiawatha configuration
# Edit hiawatha.conf and comment out or remove Tomahawk configuration
# Tomahawk = /usr/share/hiawatha/tomahawk
# TomahawkPort = 10080

# Alternatively, restrict access via firewall (local interface only)
iptables -A INPUT -p tcp --dport 10080 -s 127.0.0.1 -j DROP