CVE-2019-17544
📋 TL;DR
CVE-2019-17544 is a stack-based buffer over-read vulnerability in GNU Aspell's unescape function that occurs when processing an isolated backslash character. This allows attackers to read memory beyond the allocated buffer, potentially leading to information disclosure or crash. Systems using Aspell versions before 0.60.8 for spell checking are affected.
💻 Affected Systems
- GNU Aspell
📦 What is this software?
Ubuntu Linux by Canonical
Ubuntu Linux by Canonical
Ubuntu Linux by Canonical
Ubuntu Linux by Canonical
Ubuntu Linux by Canonical
⚠️ Risk & Real-World Impact
Worst Case
Remote code execution through memory corruption leading to complete system compromise, though this requires specific memory layout and exploitation conditions.
Likely Case
Application crash (denial of service) or information disclosure through memory leaks.
If Mitigated
Minimal impact if proper memory protections (ASLR, stack canaries) are enabled and the application runs with limited privileges.
🎯 Exploit Status
Exploitation requires triggering the vulnerable unescape function with specific input. The Chromium OSS-Fuzz project discovered and reported this vulnerability.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.60.8 and later
Vendor Advisory: https://lists.debian.org/debian-lts-announce/2019/10/msg00027.html
Restart Required: Yes
Instructions:
1. Update Aspell to version 0.60.8 or later using your package manager. 2. For Debian/Ubuntu: sudo apt update && sudo apt install aspell. 3. For source compilation: Download from GNU Aspell website and compile. 4. Restart any services using Aspell.
🔧 Temporary Workarounds
Input Validation
allSanitize input to prevent isolated backslash characters from reaching Aspell's unescape function.
Disable Aspell
allTemporarily disable Aspell functionality in applications if not critically needed.
🧯 If You Can't Patch
- Implement strict input validation to filter or escape backslash characters before passing to Aspell.
- Run applications using Aspell with reduced privileges and memory protection mechanisms enabled.
🔍 How to Verify
Check if Vulnerable:
Check Aspell version: aspell --version. If version is below 0.60.8, the system is vulnerable.Check Version:
aspell --versionVerify Fix Applied:
After updating, verify version is 0.60.8 or higher: aspell --version | grep -q '0.60.[8-9]\|0.6[1-9]\|0.[7-9]' && echo 'Patched'.📡 Detection & Monitoring
Log Indicators:
- Application crashes or segmentation faults in processes using Aspell
- Unusual memory access patterns in system logs
Network Indicators:
- None - this is a local library vulnerability
SIEM Query:
Process crashes with 'aspell' or 'libaspell' in stack trace, or memory access violations in applications using spell checking.🔗 References
- https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=16109
- https://github.com/GNUAspell/aspell/commit/80fa26c74279fced8d778351cff19d1d8f44fe4e
- https://github.com/GNUAspell/aspell/compare/rel-0.60.7...rel-0.60.8
- https://lists.debian.org/debian-lts-announce/2019/10/msg00027.html
- https://lists.debian.org/debian-lts-announce/2021/07/msg00021.html
- https://usn.ubuntu.com/4155-1/
- https://usn.ubuntu.com/4155-2/
- https://www.debian.org/security/2021/dsa-4948
- https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=16109
- https://github.com/GNUAspell/aspell/commit/80fa26c74279fced8d778351cff19d1d8f44fe4e
- https://github.com/GNUAspell/aspell/compare/rel-0.60.7...rel-0.60.8
- https://lists.debian.org/debian-lts-announce/2019/10/msg00027.html
- https://lists.debian.org/debian-lts-announce/2021/07/msg00021.html
- https://usn.ubuntu.com/4155-1/
- https://usn.ubuntu.com/4155-2/
- https://www.debian.org/security/2021/dsa-4948
