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Fencer Vulns
high 8.1

CVE-2026-85660 json

cli-mcp-server 0.2.5 Command Allowlist Bypass via Shell Substitution

published 2026-09-04 2 mo ago modified 2026-09-24 45 d ago also EUVD-2026-71116

cvss
8.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.6%
EPSS 0.6% chance of exploitation in 30 days, percentile 50%
public exploits
0
none known

Summary

cli-mcp-server 0.2.5 contains a command allowlist bypass vulnerability in the _validate_command_with_operators function when ALLOW_SHELL_OPERATORS is enabled. Attackers can use shell command substitution syntax like $(...) or backticks to execute non-allowlisted commands that bypass the ALLOWED_COMMANDS validation check.

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
total
Assessed
2 mo ago

Exploit prediction

0.62% chance of exploitation in the next 30 days, higher than 50% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/MladenSU/cli-mcp-server/issues/17 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 9.2 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N
CNA 3.1 8.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
CNA 4.0 9.2 CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • MladenSU cli-mcp-server

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.