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Fencer Intel
high 8.1

CVE-2021-27221 json

MikroTik RouterOS 6.47.9 allows remote authenticated ftp users to create or overwrite arbitrary .rsc files via the /export command.

published 5y ago modified 4mo ago also EUVD-2021-13986

cvss
8.1
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
4.0%
EPSS 4.0% chance of exploitation in 30 days, percentile 90%
public exploits
0
none known

Summary

MikroTik RouterOS 6.47.9 allows remote authenticated ftp users to create or overwrite arbitrary .rsc files via the /export command. NOTE: the vendor's position is that this is intended behavior because of how user policies work

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Exploit prediction

4.05% chance of exploitation in the next 30 days, higher than 90% of all scored CVEs (FIRST EPSS, 2026-11-09).

Exploits and checks

  • onovy.medium.com https://onovy.medium.com/routeros-user-with-just-ftp-policy-can-write-to-filesystem-cve-2021-27221-e3e45d780dfe referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
NVD 3.1 8.1 CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H
NVD 2.0 8.5 AV:N/AC:L/Au:S/C:N/I:C/A:C

References

Sources

Fencer Intel 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.