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Fencer Vulns
critical 9.0

CVE-2019-18839 json

FUDForum 3.0.9 is vulnerable to Stored XSS via the nlogin parameter.

published 2019-11-13 6 y ago modified 2026-06-17 4 mo ago also EUVD-2019-8540

cvss
9.0
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
5.4%
EPSS 5.4% chance of exploitation in 30 days, percentile 92%
public exploits
0
none known

Summary

FUDForum 3.0.9 is vulnerable to Stored XSS via the nlogin parameter. This may result in remote code execution. An attacker can use a user account to fully compromise the system using a POST request. When the admin visits the user information, the payload will execute. This will allow for PHP files to be written to the web root, and for code to execute on the remote server.

Exploit prediction

5.44% chance of exploitation in the next 30 days, higher than 92% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/fuzzlove/FUDforum-XSS-RCE referenced PoC, tagged "exploit" by a source, unverified
  • packetstormsecurity.com https://packetstormsecurity.com/files/155261/FUDForum-3.0.9-Code-Execution-Cross-Site-Scripting.html referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 9.0 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:H
NVD 2.0 8.5 AV:N/AC:M/Au:S/C:C/I:C/A:C

Classification

Weakness
  • CWE-78 Improper Neutralization of Special Elements used in an OS Command
  • CWE-79 Improper Neutralization of Input During Web Page Generation

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.