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Fencer Vulns
critical 9.8

CVE-2020-35729 in the critical feed json

KLog Server 2.4.1 allows OS command injection via shell metacharacters in the actions/authenticate.php user parameter.

published 2020-12-27 5 y ago modified 2026-06-17 4 mo ago also EUVD-2020-23385

cvss
9.8
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
88.1%
EPSS 88.1% chance of exploitation in 30 days, percentile 99.7%
public exploits
3
Metasploit, Exploit-DB, plus a Nuclei check

Summary

KLog Server 2.4.1 allows OS command injection via shell metacharacters in the actions/authenticate.php user parameter.

Timeline

  1. First public exploit (Metasploit exploit/linux/http/klog_server_authenticate_user_unauth_command_injection)
  2. Published

Exploit prediction

88.10% chance of exploitation in the next 30 days, higher than 99.7% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • Metasploit exploit/linux/http/klog_server_authenticate_user_unauth_command_injection Klog Server authenticate.php user Unauthenticated Command Injection metasploit exploit, excellent rank, 2020-12-27
  • EDB-49474 Klog Server 2.4.1 - Unauthenticated Command Injection (Metasploit) webapps, 2021-01-25
  • EDB-49366 Klog Server 2.4.1 - Command Injection (Unauthenticated) webapps, 2021-01-05
  • Nuclei template Klog Server <=2.41 - Unauthenticated Command Injection nuclei detection template
  • github.com https://github.com/mustgundogdu/Research/blob/main/KLOG_SERVER/README.md referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/mustgundogdu/Research/blob/main/KLOG_SERVER/Exploit_Code referenced PoC, tagged "exploit" by a source, unverified
  • packetstormsecurity.com http://packetstormsecurity.com/files/160798/Klog-Server-2.4.1-Command-Injection.html referenced PoC, tagged "exploit" by a source, unverified
  • packetstormsecurity.com http://packetstormsecurity.com/files/161123/Klog-Server-2.4.1-Command-Injection.html referenced PoC, tagged "exploit" by a source, unverified
  • packetstormsecurity.com http://packetstormsecurity.com/files/161410/Klog-Server-2.4.1-Command-Injection.html referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 9.8 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 10.0 AV:N/AC:L/Au:N/C:C/I:C/A:C

Classification

Weakness
  • CWE-78 Improper Neutralization of Special Elements used in an OS Command

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.