CVE-2026-23873 HUSTOJ is Vulnerable to Stored CSV Injection (Formula Injection) in Contest Rank Export

What is CVE-2026-23873?

CVE-2026-23873 is a medium-severity code injection vulnerability in zhblue hustoj, published on 21 Jan 2026. Any signed-in user can exploit it over the network, and only if a user opens a file or follows a link.

Official description

hustoj is an open source online judge based on PHP/C++/MySQL/Linux for ACM/ICPC and NOIP training. All versions are vulnerable to CSV Injection (Formula Injection) through the contest rank export functionality (contestrank.xls.php and admin/ranklist_export.php). The application fails to sanitize user-supplied input (specifically the "Nickname" field) before exporting it to an .xls file (which renders as an HTML table but is opened by Excel). If a malicious user sets their nickname to an Excel formula when an administrator exports and opens the rank list in Microsoft Excel, the formula will be executed. This can lead to arbitrary command execution (RCE) on the administrator's machine or data exfiltration. A fix was not available at the time of publication.

Weakness: CWE-1236

Which versions are affected by CVE-2026-23873?

It affects 1 product.

Products include Hustoj Hustoj.

How do I fix CVE-2026-23873?

No fix has been published for CVE-2026-23873 yet. Limit exposure of the affected software until one is available.

Upgrade, and never evaluate templates, expressions or code built from user input. More about Code injection.

Is CVE-2026-23873 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-23873 exists.

Other vulnerabilities in zhblue hustoj

• CVE-2026-24479 HUSTOJ has Arbitrary File Write (Zip Slip) in Problem Import Modules that leads to RCE Critical 9.3
• CVE-2025-50938 Cross-site scripting in n/a Medium 6.1
• CVE-2022-42187 Cross-site scripting in n/a Medium 6.1

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as GHSA-gqwv-v7vx-2qjw.