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Fencer Vulns
medium 6.8

CVE-2021-1398 json

Cisco IOS XE Software Arbitrary Code Execution Vulnerability

published 2021-03-24 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-6865

cvss
6.8
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.4%
EPSS 0.4% chance of exploitation in 30 days, percentile 33%
public exploits
0
none known

Summary

A vulnerability in the boot logic of Cisco IOS XE Software could allow an authenticated, local attacker with level 15 privileges or an unauthenticated attacker with physical access to execute arbitrary code on the underlying Linux operating system of an affected device. This vulnerability is due to incorrect validations of specific function arguments that are passed to the boot script. An attacker could exploit this vulnerability by tampering with a specific file, which an affected device would process during the initial boot process. On systems that are protected by the Unified Extensible Firmware Interface (UEFI) secure boot feature, a successful exploit could allow the attacker to execute unsigned code at boot time and bypass the image verification check in the secure boot process of the affected device.

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
2 y ago

Exploit prediction

0.39% chance of exploitation in the next 30 days, higher than 33% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 6.8 CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 6.8 CVSS:3.1/AV:P/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 6.9 AV:L/AC:M/Au:N/C:C/I:C/A:C

Affected products

  • Cisco Cisco IOS XE Software

Classification

Weakness
Technology feeds

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.