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VulnerabilityPublished

CVE-2026-23873: zhblue hustoj · CSV Injection

Affects zhblue hustojSource CVE Database V5

0

Not known to be exploited · CVSS 5.2 Medium.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 4.0 base score
5.2Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.5% chance of exploitation in 30 days – higher than 46% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:A/VC:N/VI:N/VA:N/SC:H/SI:H/SA:H

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 21 Jan 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponised: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

What to do

Affected software

ProductAffectedFixed in
zhbluehustojAffected
  • <=26.01.01
Fixed in–
GitHubzhblue/hustojpkg:github/zhblue/hustojOther threatsAffected
  • <=26.01.01
Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

  1. Implement input sanitization on the 'Nickname' field to neutralize any formula characters (e.g., prefixing with a single quote or removing leading '=' characters) before exporting to Excel files.
  2. Restrict the export functionality to highly trusted users or administrators only, minimizing exposure.
  3. Educate administrators to disable automatic formula execution in Excel by enabling the 'Disable automatic links' or 'Disable external content' settings.
  4. Use alternative export formats that do not interpret formulas, such as plain CSV with proper escaping or PDF exports.
  5. Monitor and audit exported files for suspicious content before opening.
  6. Consider sandboxing or opening exported files in isolated environments to limit potential damage.
  7. Engage with the hustoj community or maintainers to prioritize development of an official patch.
  8. Regularly update and patch related software components and maintain strong endpoint protection on administrative machines.

Description

CVE-2026-23873 is a medium-severity CSV Injection vulnerability affecting all versions of the open-source online judge system hustoj (<= 26.01.01). The vulnerability arises from improper sanitization of user input in the 'Nickname' field when exporting contest rankings to Excel-compatible . xls files. Malicious users can inject Excel formulas that execute upon opening the exported file by administrators, potentially leading to remote code execution or data exfiltration on the administrator's machine. Exploitation requires an attacker to have a low-privilege account and some user interaction (administrator opening the file). No patch is currently available. European organizations using hustoj for programming contests or training should be cautious, especially educational institutions and competitive programming platforms. Mitigations include disabling automatic formula execution in Excel, sanitizing user inputs before export, and restricting export functionality to trusted users.

References

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