CVE-2026-22250: Weblate wlc Client SSL Bypass Vulnerability

CVE-2026-22250 Overview

CVE-2026-22250 is a certificate validation bypass vulnerability in wlc, the Weblate command-line client that interfaces with Weblate's REST API. Prior to version 1.17.0, the SSL verification would be skipped for certain crafted URLs, potentially allowing attackers to intercept communications between the client and Weblate servers.

Critical Impact

Attackers could craft malicious URLs that bypass SSL certificate verification, potentially enabling man-in-the-middle attacks and exposure of sensitive data transmitted between the wlc client and Weblate servers.

Affected Products

• wlc (Weblate Command-Line Client) versions prior to 1.17.0
• Systems using wlc to communicate with Weblate REST API
• Development and translation workflows utilizing wlc for automation

Discovery Timeline

• 2026-01-12 - CVE CVE-2026-22250 published to NVD
• 2026-01-13 - Last updated in NVD database

Technical Details for CVE-2026-22250

Vulnerability Analysis

This vulnerability is classified under CWE-295 (Improper Certificate Validation). The wlc command-line client contains a flaw in its URL parsing logic that allows SSL certificate verification to be bypassed when specially crafted URLs are provided. This creates a significant security gap in the trust model between the client and Weblate servers.

The vulnerability requires local access and user interaction to exploit, as an attacker would need to convince a user to use a crafted URL or modify configuration to point to a malicious endpoint. The scope is changed, meaning the vulnerability can affect resources beyond its original security context, though the impact is limited to confidentiality with low severity.

Root Cause

The root cause lies in improper handling of URL parsing within the wlc client. Certain URL patterns were not properly validated before establishing SSL/TLS connections, causing the client to skip certificate verification steps. This allowed the client to accept connections to servers presenting invalid, self-signed, or mismatched certificates without warning the user.

Attack Vector

The attack vector is local, requiring an attacker to either:

1. Convince a victim to use a specially crafted URL when invoking wlc commands
2. Modify local configuration files to point to attacker-controlled endpoints
3. Position themselves in a network path where they can intercept traffic when SSL verification is bypassed

Once SSL verification is bypassed, an attacker in a man-in-the-middle position could potentially intercept API credentials, translation data, or other sensitive information exchanged with the Weblate server.

The vulnerability mechanism involves URL parsing logic that failed to properly enforce SSL certificate validation for certain URL formats. When a user provided a crafted URL to the wlc client, the SSL verification checks would be inadvertently skipped, allowing connections to proceed without proper certificate validation. For technical implementation details, refer to the GitHub Security Advisory.

Detection Methods for CVE-2026-22250

Indicators of Compromise

• Unusual wlc commands with non-standard or malformed URLs in command history or logs
• Network connections from wlc to unexpected IP addresses or domains
• Modified wlc configuration files pointing to non-standard Weblate endpoints
• SSL/TLS certificate warnings being suppressed or ignored in automation scripts

Detection Strategies

• Review wlc configuration files for URLs that deviate from expected Weblate server addresses
• Monitor network traffic for wlc connections to untrusted or unexpected endpoints
• Implement logging of all wlc command invocations with their target URLs
• Use network security monitoring to detect certificate validation failures or bypasses

Monitoring Recommendations

• Enable verbose logging for wlc operations in development and CI/CD environments
• Configure network monitoring to alert on connections to Weblate-like APIs from unexpected sources
• Audit automation scripts that invoke wlc for hardcoded or user-supplied URLs
• Implement certificate pinning at the network level where feasible

How to Mitigate CVE-2026-22250

Immediate Actions Required

• Upgrade wlc to version 1.17.0 or later immediately
• Audit all systems using wlc and verify they are using trusted, verified Weblate server URLs
• Review recent wlc command history for any suspicious or unexpected URL patterns
• Temporarily restrict wlc usage to known-good configurations until patching is complete

Patch Information

The vulnerability is fixed in wlc version 1.17.0. The fix was implemented in commit a513864ec4daad00146e6d6e039559726e256fa3. The patch ensures proper SSL certificate validation is enforced for all URL patterns, closing the bypass condition that existed in prior versions. For detailed discussion of the fix, see the GitHub Pull Request.

Workarounds

• Restrict wlc usage to only known, verified Weblate server URLs until patching is possible
• Implement network-level controls to ensure wlc connections only reach authorized Weblate servers
• Use a proxy or firewall to enforce certificate validation at the network boundary
• Avoid using wlc with user-supplied or untrusted URLs until the upgrade is complete

# Upgrade wlc to patched version
pip install --upgrade wlc>=1.17.0

# Verify installed version
wlc --version

# Ensure configuration points to trusted Weblate server
cat ~/.config/wlc