CVE-2026-2703
📋 TL;DR
This CVE describes an off-by-one vulnerability in the base64 decoding function of xlnt-community's xlnt library when parsing encrypted XLSX files. Attackers with local access could potentially cause memory corruption or crashes. Users of applications that utilize xlnt library versions up to 1.6.1 for processing encrypted Excel files are affected.
💻 Affected Systems
- xlnt-community xlnt
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Memory corruption leading to arbitrary code execution or application crash, potentially allowing privilege escalation or data leakage.
Likely Case
Application crash or denial of service when processing specially crafted encrypted XLSX files.
If Mitigated
Limited impact due to local access requirement and potential crash containment by application sandboxing.
🎯 Exploit Status
Exploit requires local access to the system. Public proof-of-concept available in GitHub repository.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Fixed in commit f2d7bf494e5c52706843cf7eb9892821bffb0734 and later versions
Vendor Advisory: https://github.com/xlnt-community/xlnt/issues/137
Restart Required: Yes
Instructions:
1. Update xlnt library to version after commit f2d7bf494e5c52706843cf7eb9892821bffb0734. 2. Rebuild applications using the library. 3. Restart affected services.
🔧 Temporary Workarounds
Disable encrypted XLSX processing
allConfigure applications to reject encrypted XLSX files or use alternative libraries for encrypted Excel file processing.
🧯 If You Can't Patch
- Implement strict file upload validation to reject encrypted XLSX files from untrusted sources.
- Run applications with minimal privileges and in sandboxed environments to limit potential damage.
🔍 How to Verify
Check if Vulnerable:
Check if your application uses xlnt library version 1.6.1 or earlier by examining dependencies or build configurations.Check Version:
Check build configuration or package manager for xlnt version (e.g., 'apt list --installed | grep xlnt' on Debian-based systems)Verify Fix Applied:
Verify the xlnt library version includes commit f2d7bf494e5c52706843cf7eb9892821bffb0734 or later.📡 Detection & Monitoring
Log Indicators:
- Application crashes when processing encrypted Excel files
- Memory access violation errors in application logs
SIEM Query:
Application logs containing 'xlnt', 'base64', or 'encrypted XLSX' with error/crash indicators🔗 References
- https://github.com/oneafter/0128/blob/main/xl1/repro
- https://github.com/xlnt-community/xlnt/
- https://github.com/xlnt-community/xlnt/commit/f2d7bf494e5c52706843cf7eb9892821bffb0734
- https://github.com/xlnt-community/xlnt/issues/137
- https://vuldb.com/?ctiid.346649
- https://vuldb.com/?id.346649
- https://vuldb.com/?submit.754377
