CVE-2026-23873: hustoj is an open source online judge based on PHP/C++/MySQL/Linux for ACM/ICPC and NOIP training

Q: How do I fix CVE-2026-23873?

hustoj: upgrade to newer than 26.01.31. Exact commands for each OS are on this page.

Q: Is CVE-2026-23873 being exploited?

CVE-2026-23873 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-23873 affect?

CVE-2026-23873 affects hustoj. Severity is critical (CVSS 9.0). 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

Q: How urgent is CVE-2026-23873?

Priority 53/100. Critical severity; Public exploit reference; On your watchlist

This month

CRITICAL 9.0WATCHLISTUPGRADE

CVE-2026-23873 is a critical-severity flaw (CVSS 9.0) affecting hustoj. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

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

Why this priority

Critical severity
Public exploit reference
On your watchlist

A fixed release or distro patch exists.

Risk facts

CVSS score	9.0 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	Low
User interaction	Required
EPSS exploit chance	0.6% (top 53%)
CISA exploited list	No
Weakness	CWE-1236
Published	2026-01-22
Last modified	2026-06-17

Publisher (CNA): GitHub, Inc. · Vendor: hustoj

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-01-22 00:15 UTCPublished CVE record published
2026-06-17 10:22 UTCUpdated Record last modified

hustoj hustoj UPGRADE

Affected: <= 26.01.31

Fixed in: newer than 26.01.31

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy hustoj || rpm -q hustoj || hustoj --version

2. UPGRADE to newer than 26.01.31 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade hustoj

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade hustoj

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-23873?

hustoj: upgrade to newer than 26.01.31. Exact commands for each OS are on this page.

Is CVE-2026-23873 being exploited?

CVE-2026-23873 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-23873 affect?

CVE-2026-23873 affects hustoj. Severity is critical (CVSS 9.0). 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

How urgent is CVE-2026-23873?

Priority 53/100. Critical severity; Public exploit reference; On your watchlist

Software pages

PHP vulnerabilities · MySQL vulnerabilities

Related CVEs

CVE-2026-24479 CRITICAL 9.8 UPGRADE HUSTOF is an open source online judge based on PHP/C++/MySQL/Linux for ACM/ICPC and NOIP training
CVE-2025-50938 MEDIUM 6.1 DOWNGRADE Cross site scripting (XSS) vulnerability in Hustoj 2025-01-31 via the TID parameter to thread.php.

References

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