CVE-2023-34795
📋 TL;DR
CVE-2023-34795 is a use-after-free vulnerability in xlsxio library versions 0.1.2 to 0.2.34 where the xlsxioread_sheetlist_close() function frees an uninitialized pointer. Attackers can exploit this by providing a crafted XLSX file to cause a Denial of Service (DoS) crash. Any application using vulnerable xlsxio versions to parse XLSX files is affected.
💻 Affected Systems
- xlsxio
📦 What is this software?
Xlsxio by Xlsxio Project
⚠️ Risk & Real-World Impact
Worst Case
Complete application crash leading to sustained Denial of Service, potentially disrupting business operations if the application is critical.
Likely Case
Application crashes when processing malicious XLSX files, causing temporary service disruption until restart.
If Mitigated
Application crashes but auto-restarts or load balancing prevents sustained outage; no data compromise occurs.
🎯 Exploit Status
Exploitation requires only a crafted XLSX file; no authentication needed if file upload/processing is available.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 0.2.35 and later
Vendor Advisory: https://github.com/brechtsanders/xlsxio/commit/d653f1604b54532f11b45dca1fa164b4a1f15e2d
Restart Required: Yes
Instructions:
1. Update xlsxio to version 0.2.35 or later. 2. Recompile any applications using xlsxio. 3. Restart affected services.
🔧 Temporary Workarounds
Disable XLSX file processing
allTemporarily block or reject XLSX file uploads/processing in applications.
Input validation
allImplement strict file type validation and sanitization for uploaded XLSX files.
🧯 If You Can't Patch
- Implement network segmentation to isolate vulnerable systems from untrusted networks.
- Deploy application-level firewalls to inspect and block malicious XLSX files.
🔍 How to Verify
Check if Vulnerable:
Check xlsxio library version: 'xlsxio_read --version' or examine library files. Verify if version is between 0.1.2 and 0.2.34.Check Version:
xlsxio_read --version 2>/dev/null || grep -r "xlsxio" /usr/include /usr/local/include 2>/dev/null | grep -i versionVerify Fix Applied:
Confirm xlsxio version is 0.2.35 or later. Test with known safe XLSX files to ensure functionality.📡 Detection & Monitoring
Log Indicators:
- Application crashes with segmentation faults when processing XLSX files
- Unexpected process termination logs
Network Indicators:
- Multiple failed file upload attempts
- Unusual XLSX file upload patterns
SIEM Query:
source="application.logs" AND ("segmentation fault" OR "crash") AND "xlsx"🔗 References
- https://github.com/brechtsanders/xlsxio/commit/d653f1604b54532f11b45dca1fa164b4a1f15e2d
- https://github.com/brechtsanders/xlsxio/issues/121
- https://github.com/xf1les/cve-advisories/blob/main/2023/CVE-2023-34795.md
- https://github.com/brechtsanders/xlsxio/commit/d653f1604b54532f11b45dca1fa164b4a1f15e2d
- https://github.com/brechtsanders/xlsxio/issues/121
- https://github.com/xf1les/cve-advisories/blob/main/2023/CVE-2023-34795.md
