CVE-2021-30499
📋 TL;DR
CVE-2021-30499 is a buffer overflow vulnerability in libcaca's export_troff function that could allow memory corruption. This affects systems using libcaca for ASCII art rendering, potentially enabling arbitrary code execution or denial of service. Users of affected libcaca versions across multiple Linux distributions are vulnerable.
💻 Affected Systems
- libcaca
📦 What is this software?
Fedora by Fedoraproject
Fedora by Fedoraproject
Fedora by Fedoraproject
Libcaca by Libcaca Project
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution leading to complete system compromise if libcaca processes untrusted input from network sources.
Likely Case
Application crash or denial of service when processing malformed input, potentially leading to privilege escalation in specific contexts.
If Mitigated
Limited impact with proper input validation and sandboxing, potentially only causing application termination.
🎯 Exploit Status
Exploitation requires crafting specific input to trigger the buffer overflow in export_troff function.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.99.beta20 and later
Vendor Advisory: https://bugzilla.redhat.com/show_bug.cgi?id=1948679
Restart Required: Yes
Instructions:
1. Update libcaca package using system package manager. 2. For Fedora: sudo dnf update libcaca. 3. For Debian/Ubuntu: sudo apt update && sudo apt upgrade libcaca. 4. Restart affected applications using libcaca.
🔧 Temporary Workarounds
Disable troff export functionality
linuxRemove or restrict access to libcaca's troff export feature if not required.
Input validation and sanitization
allImplement strict input validation for any data passed to libcaca functions.
🧯 If You Can't Patch
- Implement strict input validation and sanitization for all data processed by libcaca
- Run libcaca applications with minimal privileges and in isolated environments
🔍 How to Verify
Check if Vulnerable:
Check libcaca version: dpkg -l libcaca0 or rpm -q libcaca. If version is earlier than 0.99.beta20, system is vulnerable.Check Version:
dpkg -l libcaca0 2>/dev/null || rpm -q libcaca 2>/dev/null || echo 'libcaca not found'Verify Fix Applied:
Verify updated version: dpkg -l libcaca0 | grep 0.99.beta20 or later, or rpm -q libcaca | grep 0.99.beta20.📡 Detection & Monitoring
Log Indicators:
- Application crashes involving libcaca
- Segmentation faults in processes using libcaca
- Abnormal termination of ASCII art rendering applications
Network Indicators:
- Unusual input patterns to applications using libcaca
SIEM Query:
process.name:libcaca AND (event.type:crash OR signal.name:SIGSEGV)🔗 References
- https://bugzilla.redhat.com/show_bug.cgi?id=1948679
- https://github.com/cacalabs/libcaca/issues/54
- https://lists.debian.org/debian-lts-announce/2024/04/msg00004.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6WFGYICNTMNDNMDDUV4G2RYFB5HNJCOV/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PC7EGOEQ5C4OD66ZUJJIIYEXBTZOCMZX/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZSBCRN6EGQJUVOSD4OEEQ6XORHEM2CUL/
- https://bugzilla.redhat.com/show_bug.cgi?id=1948679
- https://github.com/cacalabs/libcaca/issues/54
- https://lists.debian.org/debian-lts-announce/2024/04/msg00004.html
- https://lists.debian.org/debian-lts-announce/2025/07/msg00019.html
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/6WFGYICNTMNDNMDDUV4G2RYFB5HNJCOV/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/PC7EGOEQ5C4OD66ZUJJIIYEXBTZOCMZX/
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/ZSBCRN6EGQJUVOSD4OEEQ6XORHEM2CUL/
