CVE-2019-25544: Pidgin DOS Vulnerability

CVE-2019-25544 Overview

CVE-2019-25544 is a denial of service vulnerability affecting Pidgin 2.13.0, a popular open-source instant messaging client. The vulnerability allows local attackers to crash the application by providing an excessively long username string during account creation. When an attacker inputs a buffer of 1000 characters in the username field and subsequently joins a chat, the application crashes, rendering it unavailable to the user.

Critical Impact

Local attackers can cause complete application unavailability by exploiting improper input validation in the username field, leading to denial of service conditions for Pidgin users.

Affected Products

• Pidgin 2.13.0

Discovery Timeline

• 2026-03-21 - CVE CVE-2019-25544 published to NVD
• 2026-03-23 - Last updated in NVD database

Technical Details for CVE-2019-25544

Vulnerability Analysis

This denial of service vulnerability stems from improper handling of user-supplied input in Pidgin's account creation functionality. The application fails to properly validate the length of the username string, allowing attackers to provide an excessively long input that triggers a crash condition. The vulnerability is classified under CWE-807 (Reliance on Untrusted Inputs in a Security Decision), indicating that the application makes security-relevant decisions based on input that can be manipulated by attackers.

The local attack vector requires the attacker to have access to the Pidgin application on the target system. While this limits the attack surface compared to remote vulnerabilities, it still poses a significant risk in shared computing environments or where malicious users have local access.

Root Cause

The root cause of this vulnerability lies in insufficient input validation within Pidgin's username handling mechanism. The application does not enforce appropriate length restrictions on the username field during account creation, allowing users to input strings far exceeding expected boundaries. When a username containing 1000 characters is processed during chat join operations, the application encounters an unhandled condition that results in a crash.

Attack Vector

The attack is executed locally by interacting with the Pidgin application's user interface. An attacker creates a new account and enters an excessively long username string (approximately 1000 characters) in the username field. Upon attempting to join a chat with this malformed account configuration, the application crashes due to improper handling of the oversized input.

The vulnerability requires no special privileges to exploit, making it accessible to any user with local access to the Pidgin application. The impact is limited to availability—there is no evidence of confidentiality or integrity compromise associated with this vulnerability.

Detection Methods for CVE-2019-25544

Indicators of Compromise

• Unexpected Pidgin application crashes, particularly when joining chat rooms
• Presence of abnormally long usernames (exceeding typical limits) in account configurations
• Repeated application restarts following chat join attempts

Detection Strategies

• Monitor for Pidgin process crashes and abnormal terminations in system logs
• Implement endpoint detection rules to alert on repeated application failures
• Review account configuration files for usernames exceeding reasonable length thresholds

Monitoring Recommendations

• Enable crash reporting and logging for desktop applications including Pidgin
• Monitor system stability metrics on workstations where Pidgin is deployed
• Implement application-level monitoring to detect denial of service patterns

How to Mitigate CVE-2019-25544

Immediate Actions Required

• Upgrade Pidgin to a version newer than 2.13.0 where input validation has been improved
• Review existing account configurations for abnormally long usernames
• Consider temporarily restricting Pidgin usage in shared computing environments until patched

Patch Information

Organizations using Pidgin 2.13.0 should upgrade to the latest available version. Additional technical details and security advisories can be found at the Pidgin Official Website. The VulnCheck Pidgin DoS Advisory provides further information about this vulnerability.

Technical details about the exploitation method are documented in Exploit-DB #46930.

Workarounds

• Enforce administrative policies limiting username length at the organizational level
• Monitor and audit account configurations for excessively long usernames
• In multi-user environments, restrict account creation privileges to trusted administrators
• Consider using alternative messaging clients until the application can be upgraded

# Configuration example
# Verify installed Pidgin version
pidgin --version

# Check for account configuration files with long usernames
grep -r "username" ~/.purple/accounts.xml | awk '{if(length($0) > 100) print}'