4.7

CVE-2021-27853: cisco catalyst_6503-e_firmware Authentication Bypass by Spoofing

CVSS: 4.7v3.1MediumModified
Published 27-09-2022Last modified 04-11-2025
Open JSON

Vulnerability summary

CVE-2021-27853 is a medium (CVSS 4.7) Authentication Bypass by Spoofing vulnerability in cisco catalyst_6503-e_firmware. EPSS estimates a 0.81% chance of exploitation in the next 30 days, higher than 56.2% of scored vulnerabilities. 1 public exploit is recorded.

Overall risk
29/100
0100
Medium · default modelHow is this calculated?
CVSS score
4.7/10
010
Medium · v3.1 (CVE.org)
EPSS score
0.81%
0%100%
Low · +0.06 pp in 30 days
KEVNot listedIn no KEV catalog
RansomwareNone recordedNo known use recorded
Public exploits1reference

Timeline

  1. 27-09-2022
    PublishedVulnerability first disclosed.
  2. 04-11-2025
    Last modifiedVulnerability information updated.

Description

Layer 2 network filtering capabilities such as IPv6 RA guard or ARP inspection can be bypassed using combinations of VLAN 0 headers and LLC/SNAP headers.

CVSS metrics

2 scores · 2 sources · 1 version

EPSS trend

Probability

0.81%

Chance of exploitation in the next 30 days

Percentile

56%

Versus all other CVEs

30-day change

+0.06 pp

From 0.76% on 18-09-2026

18-09-202618-10-2026
EPSS score
0.81%

Known exploited

Compare KEV catalogs

Not in any of the 3 tracked catalogs.

Public exploits

1 found
  • referenceUnverified

    Exploit Reference (blog.champtar.fr)

    Maturity: unknown

Weaknesses

CWE · root cause

Affected systems

Cisco94 products
Ieee2 products
Ietf2 products

3 vendors · 98 products

References

7 links