CVE-2025-5264
📋 TL;DR
This vulnerability in Firefox and Thunderbird's 'Copy as cURL' feature allows command injection via insufficient newline character escaping. An attacker can trick users into executing malicious curl commands, potentially leading to local code execution. Affected users include those running vulnerable versions of Firefox, Firefox ESR, and Thunderbird.
💻 Affected Systems
- Firefox
- Firefox ESR
- Thunderbird
📦 What is this software?
Firefox by Mozilla
Firefox by Mozilla
Firefox by Mozilla
⚠️ Risk & Real-World Impact
Worst Case
Full local code execution with user privileges, allowing file system access, data theft, and further system compromise.
Likely Case
Limited command execution in user context, potentially stealing cookies, session data, or executing scripts.
If Mitigated
No impact if users don't execute untrusted curl commands or have updated software.
🎯 Exploit Status
Exploitation requires social engineering to trick users into executing malicious commands. No authentication needed for initial attack vector.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Firefox 139+, Firefox ESR 115.24+, Firefox ESR 128.11+, Thunderbird 139+, Thunderbird 128.11+
Vendor Advisory: https://www.mozilla.org/security/advisories/mfsa2025-42/
Restart Required: Yes
Instructions:
1. Open Firefox/Thunderbird. 2. Click menu → Help → About Firefox/Thunderbird. 3. Allow automatic update check and installation. 4. Restart browser when prompted.
🔧 Temporary Workarounds
Disable 'Copy as cURL' feature
allRemove or disable the developer tool feature that generates curl commands
Not applicable - requires browser configuration changes
User awareness training
allTrain users not to execute untrusted curl commands from unknown sources
🧯 If You Can't Patch
- Implement application whitelisting to prevent execution of curl with malicious parameters
- Use network segmentation to limit impact and monitor for suspicious curl command execution
🔍 How to Verify
Check if Vulnerable:
Check browser version in About dialog. If version is below patched versions listed, system is vulnerable.Check Version:
firefox --version or thunderbird --version on command lineVerify Fix Applied:
Verify browser version is at or above patched versions after update.📡 Detection & Monitoring
Log Indicators:
- Unusual curl command execution with newline characters
- Multiple curl processes spawned from browser
Network Indicators:
- Suspicious curl requests to unexpected domains
- Unusual command and control traffic following curl execution
SIEM Query:
process.name='curl' AND command_line CONTAINS '\n' AND parent_process.name CONTAINS 'firefox'🔗 References
- https://bugzilla.mozilla.org/show_bug.cgi?id=1950001
- https://www.mozilla.org/security/advisories/mfsa2025-42/
- https://www.mozilla.org/security/advisories/mfsa2025-43/
- https://www.mozilla.org/security/advisories/mfsa2025-44/
- https://www.mozilla.org/security/advisories/mfsa2025-45/
- https://www.mozilla.org/security/advisories/mfsa2025-46/
- https://lists.debian.org/debian-lts-announce/2025/05/msg00043.html
- https://lists.debian.org/debian-lts-announce/2025/05/msg00046.html
