How severe is CVE-2026-23873?

CVE-2026-23873 has a CVSS 3.x base score of 9.0, rated critical severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.

Is CVE-2026-23873 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (40th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-23873?

CVE-2026-23873 affects Hustoj. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-23873?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-23873 have an EU (EUVD) identifier?

Yes. CVE-2026-23873 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-4200.

When was CVE-2026-23873 published?

CVE-2026-23873 was published on 2026-01-22 and last updated on 2026-06-17.

CVE-2026-23873

CVE-2026-23873 is a critical-severity vulnerability in Hustoj with a CVSS 3.x base score of 9.0. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-1236.

Key facts

Severity: Critical (CVSS 3.x base score 9.0)
CVSS v4: 5.2
EPSS exploit prediction: 1% (40th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-4200
Weakness: CWE-1236
Affected product: Hustoj
Published: 2026-01-22
Last modified: 2026-06-17

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.

Frequently asked questions

What is CVE-2026-23873?: 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.
How severe is CVE-2026-23873?: CVE-2026-23873 has a CVSS 3.x base score of 9.0, rated critical severity. It is exploitable over network with low attack complexity, requires low privileges and user interaction. Impact on confidentiality is high, integrity high, and availability high.
Is CVE-2026-23873 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (40th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-23873?: CVE-2026-23873 affects Hustoj. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-23873?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-23873 have an EU (EUVD) identifier?: Yes. CVE-2026-23873 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-4200.
When was CVE-2026-23873 published?: CVE-2026-23873 was published on 2026-01-22 and last updated on 2026-06-17.

References

https://github.com/zhblue/hustoj/security/advisories/GHSA-gqwv-v7vx-2qjw

Affected products (1)

cpe:2.3:a:hustoj:hustoj:*:*:*:*:*:*:*:*

More vulnerabilities in Hustoj

CVE-2026-24479 — Critical (CVSS 9.8): HUSTOF is an open source online judge based on PHP/C++/MySQL/Linux for ACM/ICPC and NOIP training. Prior to version…
CVE-2025-50938 — Medium (CVSS 6.1): Cross site scripting (XSS) vulnerability in Hustoj 2025-01-31 via the TID parameter to thread.php.
CVE-2022-42187 — Medium (CVSS 6.1): Hustoj 22.09.22 has a XSS Vulnerability in /admin/problem_judge.php.

All CVEs affecting Hustoj →

Other CWE-1236 (Improper Neutralization of Formula Elements in a CSV File) vulnerabilities

CVE-2026-31049 — Critical (CVSS 9.8): An issue in Hostbill v.2025-11-24 and 2025-12-01 allows a remote attacker to execute arbitrary code and escalate…
CVE-2020-36962 — Critical (CVSS 9.8): Tendenci 12.3.1 contains a CSV formula injection vulnerability in the contact form message field that allows attackers…
CVE-2021-47901 — Critical (CVSS 9.8): Dirsearch 0.4.1 contains a CSV injection vulnerability when using the --csv-report flag that allows attackers to inject…
CVE-2020-36941 — Critical (CVSS 9.8): Knockpy 4.1.1 contains a CSV injection vulnerability that allows attackers to inject malicious formulas into CSV…
CVE-2025-56267 — Critical (CVSS 9.8): A CSV injection vulnerability in the /id_profiles endpoint of Avigilon ACM v7.10.0.20 allows attackers to execute…
CVE-2023-47295 — Critical (CVSS 9.8): A CSV injection vulnerability in NCR Terminal Handler v1.5.1 allows attackers to execute arbitrary commands via…

Browse all CWE-1236 (Improper Neutralization of Formula Elements in a CSV File) vulnerabilities →