CVE-2015-1877
📋 TL;DR
This vulnerability in xdg-open allows remote attackers to execute arbitrary commands by tricking users into opening a malicious file. It affects Debian systems using dash shell with xdg-utils 1.1.0 rc1. The flaw stems from improper handling of local variables in the open_generic_xdg_mime function.
💻 Affected Systems
- xdg-utils
📦 What is this software?
Xdg Utils by Freedesktop
⚠️ Risk & Real-World Impact
Worst Case
Full system compromise via remote code execution with user privileges, potentially leading to privilege escalation, data theft, or complete system takeover.
Likely Case
Local privilege escalation or arbitrary command execution when a user opens a malicious file, potentially leading to malware installation or data exfiltration.
If Mitigated
Limited impact with proper user education about opening untrusted files and network segmentation reducing attack surface.
🎯 Exploit Status
Exploitation requires user interaction (opening a malicious file). Proof of concept code was published in security advisories.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: xdg-utils 1.1.0-1+deb8u1 or later
Vendor Advisory: http://www.debian.org/security/2015/dsa-3165
Restart Required: No
Instructions:
1. Update package: sudo apt-get update && sudo apt-get install xdg-utils
2. Verify version: dpkg -l xdg-utils | grep ^ii
3. Ensure version is 1.1.0-1+deb8u1 or higher
🔧 Temporary Workarounds
Change default shell
linuxTemporarily change default shell from dash to bash to avoid the vulnerability
sudo dpkg-reconfigure dash
Select 'No' when prompted to use dash as default shell
Disable xdg-open
linuxRemove or restrict xdg-open execution permissions
sudo chmod -x /usr/bin/xdg-open
sudo mv /usr/bin/xdg-open /usr/bin/xdg-open.disabled
🧯 If You Can't Patch
- Implement strict file handling policies: block execution of untrusted files and educate users about risks
- Use application whitelisting to prevent unauthorized command execution and monitor for suspicious xdg-open activity
🔍 How to Verify
Check if Vulnerable:
Check xdg-utils version and shell: dpkg -l xdg-utils | grep '1.1.0 rc1' && readlink -f /bin/sh | grep dashCheck Version:
dpkg -l xdg-utils | grep ^iiVerify Fix Applied:
Verify updated version: dpkg -l xdg-utils | grep -E '1.1.0-1\+deb8u1|1.1.1'📡 Detection & Monitoring
Log Indicators:
- Unusual xdg-open processes spawning shells
- Suspicious command execution following file opens
- Failed privilege escalation attempts
Network Indicators:
- Outbound connections from xdg-open processes
- Unexpected network activity after file operations
SIEM Query:
process_name:xdg-open AND (child_process:bash OR child_process:sh OR child_process:dash)🔗 References
- http://www.debian.org/security/2015/dsa-3165
- http://www.openwall.com/lists/oss-security/2015/02/18/7
- http://www.openwall.com/lists/oss-security/2015/02/18/9
- http://www.securityfocus.com/bid/72675
- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=777722
- https://bugs.freedesktop.org/show_bug.cgi?id=89129
- http://www.debian.org/security/2015/dsa-3165
- http://www.openwall.com/lists/oss-security/2015/02/18/7
- http://www.openwall.com/lists/oss-security/2015/02/18/9
- http://www.securityfocus.com/bid/72675
- https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=777722
- https://bugs.freedesktop.org/show_bug.cgi?id=89129
