CVE-2024-38428: GNU Wget URI Parsing Vulnerability

CVE-2024-38428 Overview

CVE-2024-38428 is a URI parsing vulnerability in GNU Wget through version 1.24.5 that affects how semicolons are handled in the userinfo subcomponent of a URI. The flaw in url.c causes data intended for the userinfo subcomponent to be misinterpreted as part of the host subcomponent, potentially leading to insecure behavior. This Input Validation Error can result in requests being sent to unintended hosts, enabling data exfiltration or man-in-the-middle attacks.

Critical Impact

Attackers can exploit this URI parsing flaw to redirect Wget requests to malicious hosts, potentially exposing sensitive credentials or enabling server-side request forgery attacks.

Affected Products

• GNU Wget through version 1.24.5
• Systems and applications utilizing GNU Wget for automated downloads
• Linux distributions packaging vulnerable Wget versions

Discovery Timeline

• 2024-06-16 - CVE-2024-38428 published to NVD
• 2025-04-21 - Last updated in NVD database

Technical Details for CVE-2024-38428

Vulnerability Analysis

The vulnerability stems from improper parsing logic in url.c within GNU Wget. When processing URIs containing semicolons in the userinfo subcomponent (the portion before the @ symbol that typically contains username and password), Wget incorrectly interprets the semicolon as a delimiter. This causes portions of the userinfo data to be parsed as part of the host subcomponent instead.

According to RFC 3986, the userinfo subcomponent can contain semicolons as valid characters. However, Wget's parsing implementation fails to properly handle this case, leading to boundary confusion between URI components. This misinterpretation can cause Wget to connect to an attacker-controlled host rather than the intended destination.

The vulnerability enables network-based attacks without requiring authentication or user interaction, making it exploitable in automated scripting environments where Wget is commonly used.

Root Cause

The root cause is an Input Validation Error in the URI parsing logic within url.c. The code fails to properly distinguish between semicolons used within the userinfo subcomponent and other URI delimiters. This leads to Interpretation Conflict (CWE-436), where the same data is interpreted differently than intended by the URI specification.

Attack Vector

An attacker can craft a malicious URI with a semicolon in the userinfo subcomponent that causes Wget to misinterpret the intended host. When a victim application or script passes this malformed URI to Wget, the tool connects to an attacker-controlled server instead of the legitimate destination.

This attack vector is particularly dangerous in scenarios where:

• Scripts automatically download files from user-supplied URLs
• CI/CD pipelines use Wget for fetching dependencies
• Web applications proxy requests through Wget
• Automated backup or synchronization systems rely on Wget

The vulnerability requires no special privileges or user interaction, making it suitable for exploitation in headless environments.

Detection Methods for CVE-2024-38428

Indicators of Compromise

• Unexpected network connections to unknown hosts originating from Wget processes
• Download logs showing connections to hosts different from the apparent URL targets
• Anomalous outbound traffic patterns from systems running automated Wget scripts
• Error logs indicating connection failures to legitimate hosts followed by successful connections elsewhere

Detection Strategies

• Monitor network traffic for Wget user-agent connections to unexpected destinations
• Implement URL validation and sanitization before passing URLs to Wget
• Deploy network-level monitoring to detect semicolon-based URI manipulation attempts
• Review Wget command logs for URIs containing semicolons in suspicious positions

Monitoring Recommendations

• Enable verbose logging for Wget operations to capture full URI parsing details
• Configure intrusion detection systems to flag unusual Wget connection patterns
• Implement egress filtering to restrict Wget connections to approved destinations
• Set up alerts for Wget processes connecting to IP addresses or newly registered domains

How to Mitigate CVE-2024-38428

Immediate Actions Required

• Update GNU Wget to a patched version that addresses the URI parsing flaw
• Audit scripts and applications that utilize Wget with user-controlled URLs
• Implement input validation to sanitize URLs before passing them to Wget
• Consider using alternative download utilities with proper URI parsing until patched

Patch Information

The GNU Wget development team has addressed this vulnerability in commit ed0c7c7e0e8f7298352646b2fd6e06a11e242ace. Organizations should update to the patched version as soon as available in their distribution's package repositories. Additional security advisories have been issued by Debian LTS and NetApp.

For technical details on the fix, refer to the GNU Wget Commit Update and the GNU Wget Bug Report.

Workarounds

• Validate and sanitize all URLs before passing them to Wget, rejecting those with semicolons in the userinfo section
• Use URL encoding for special characters in userinfo to avoid parsing ambiguity
• Implement a wrapper script that parses and validates URLs before invoking Wget
• Consider using curl as an alternative until Wget is patched, as it may handle this edge case differently

# URL validation wrapper for Wget
# Reject URLs with semicolons in userinfo to mitigate CVE-2024-38428
validate_url() {
    local url="$1"
    # Extract userinfo portion and check for semicolons
    if echo "$url" | grep -qE '^[a-z]+://[^@]*;[^@]*@'; then
        echo "Warning: URL contains semicolon in userinfo - potential CVE-2024-38428 exploit"
        return 1
    fi
    wget "$url"
}