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CVE-2015-8833

9.8 CRITICAL
Remote Code Execution

📋 TL;DR

This is a critical use-after-free vulnerability in the pidgin-otr plugin for Pidgin instant messaging client. Attackers can execute arbitrary code remotely by tricking users into clicking the 'Authenticate buddy' menu item. Users of Pidgin with the OTR plugin are affected.

💻 Affected Systems

Products:
  • pidgin-otr plugin for Pidgin
Versions: All versions before 4.0.2
Operating Systems: Linux, Windows, macOS - any OS running Pidgin with OTR plugin
Default Config Vulnerable: ⚠️ Yes
Notes: Requires the OTR plugin to be installed and enabled in Pidgin. The vulnerability triggers when user interacts with the 'Authenticate buddy' menu item.

📦 What is this software?

Pidgin Otr by Cypherpunks

View all CVEs affecting Pidgin Otr →

⚠️ Risk & Real-World Impact

🔴

Worst Case

Remote code execution with the privileges of the Pidgin user, potentially leading to full system compromise, data theft, and lateral movement.

🟠

Likely Case

Remote code execution leading to malware installation, credential theft, and system compromise.

🟢

If Mitigated

Limited impact if proper network segmentation and least privilege principles are followed, though local compromise still possible.

🌐 Internet-Facing: HIGH - Attackers can exploit remotely via crafted messages without authentication.
🏢 Internal Only: HIGH - Internal attackers or compromised systems can exploit via internal messaging.

🎯 Exploit Status

Public PoC: ⚠️ Yes
Weaponized: LIKELY
Unauthenticated Exploit: ⚠️ Yes
Complexity: LOW

Exploitation requires user interaction (clicking menu item), but the attack vector is simple and reliable once triggered.

🛠️ Fix & Mitigation

✅ Official Fix

Patch Version: 4.0.2

Vendor Advisory: http://www.openwall.com/lists/oss-security/2016/03/09/8

Restart Required: Yes

Instructions:

1. Update pidgin-otr plugin to version 4.0.2 or later. 2. Restart Pidgin. 3. For Linux distributions, use package manager: 'sudo apt-get update && sudo apt-get install pidgin-otr' (Debian/Ubuntu) or 'sudo yum update pidgin-otr' (RHEL/CentOS). 4. For Windows/macOS, download from official Pidgin website.

🔧 Temporary Workarounds

Disable OTR plugin

all

Temporarily disable the OTR plugin in Pidgin to prevent exploitation

In Pidgin: Tools > Plugins > Uncheck 'Off-the-Record Messaging'

Block malicious messages

all

Configure Pidgin to only accept messages from trusted contacts

In Pidgin: Buddies > Show > Only from buddies

🧯 If You Can't Patch

  • Remove the pidgin-otr plugin completely from Pidgin installation
  • Run Pidgin with reduced privileges (non-admin/non-root account)

🔍 How to Verify

Check if Vulnerable:

Check pidgin-otr plugin version in Pidgin: Tools > Plugins > Off-the-Record Messaging > Version. If version is below 4.0.2, system is vulnerable.

Check Version:

On Linux: 'dpkg -l | grep pidgin-otr' or 'rpm -qa | grep pidgin-otr'. On Windows: Check plugin version in Pidgin GUI.

Verify Fix Applied:

Verify pidgin-otr plugin version is 4.0.2 or higher in Pidgin plugin manager.

📡 Detection & Monitoring

Log Indicators:

  • Pidgin crash logs with memory access violations
  • Unexpected process execution from Pidgin context

Network Indicators:

  • Unusual network connections originating from Pidgin process
  • Suspicious incoming messages triggering authentication requests

SIEM Query:

Process creation where parent process is pidgin.exe or pidgin binary AND (command line contains suspicious patterns OR destination IP is malicious)

📊 Metadata

CVE ID: CVE-2015-8833
CVSS v3 Score: 9.8 (CRITICAL)
CVSS Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published: April 12, 2016
Last Updated: April 12, 2025

🔗 References

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