PHP
CVE-2026-23873
CRITICAL
Severity by source
AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
Primary rating from GitHub Advisory · only source for this CVE.
CVSS VectorGitHub Advisory
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
Lifecycle Timeline
3DescriptionGitHub Advisory
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.
AnalysisAI
HUSTOJ online judge system has a CSV injection vulnerability in all versions that allows code execution through crafted submissions exported to spreadsheets.
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | Authenticated user account required to set malicious Nickname field. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | CVSS 9.0 with PoC. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | A participant submits a solution containing a CSV formula payload in the username or code comments. When an admin exports results to CSV and opens in Excel, the formula executes, potentially stealing credentials or installing malware. |
| Remediation | Sanitize CSV exports by prefixing cells with a single quote. … Detailed patch versions, workarounds, and compensating controls in full report. |
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