Skip to content
Fencer Vulns
high 8.1

CVE-2021-34739 json

Cisco Small Business Series Switches Session Credentials Replay Vulnerability

published 2021-11-04 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-21389

cvss
8.1
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
1.7%
EPSS 1.7% chance of exploitation in 30 days, percentile 76%
public exploits
0
none known

Summary

A vulnerability in the web-based management interface of multiple Cisco Small Business Series Switches could allow an unauthenticated, remote attacker to replay valid user session credentials and gain unauthorized access to the web-based management interface of an affected device. This vulnerability is due to insufficient expiration of session credentials. An attacker could exploit this vulnerability by conducting a man-in-the-middle attack against an affected device to intercept valid session credentials and then replaying the intercepted credentials toward the same device at a later time. A successful exploit could allow the attacker to access the web-based management interface with administrator privileges.

Patch / fix

  • cisco sf500-24_firmware 2.5.8.12
  • cisco sf500-24p_firmware 2.5.8.12
  • cisco sf500-24mp_firmware 2.5.8.12
  • cisco sf500-48_firmware 2.5.8.12
  • cisco sf500-48p_firmware 2.5.8.12
  • cisco sf500-48mp_firmware 2.5.8.12
  • cisco sg500-28_firmware 2.5.8.12
  • cisco sg500-28p_firmware 2.5.8.12
  • cisco sg500-28mpp_firmware 2.5.8.12
  • cisco sg500-52_firmware 2.5.8.12
  • cisco sg500-52p_firmware 2.5.8.12
  • cisco sg500-52mp_firmware 2.5.8.12
  • cisco sg500x-24_firmware 2.5.8.12
  • cisco sg500x-24p_firmware 2.5.8.12
  • cisco sg500x-24mpp_firmware 2.5.8.12
  • cisco sg500x-48_firmware 2.5.8.12
  • cisco sg500x-48p_firmware 2.5.8.12
  • cisco sg500x-48mp_firmware 2.5.8.12
  • cisco sg500xg-8f8t_firmware 2.5.8.12

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
total
Assessed
2 y ago

Exploit prediction

1.67% chance of exploitation in the next 30 days, higher than 76% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 3.1 8.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 3.1 8.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
NVD 2.0 6.8 AV:N/AC:M/Au:N/C:P/I:P/A:P

Affected products

  • Cisco Cisco Small Business Smart and Managed Switches

Classification

Weakness
  • CWE-613 DEPRECATED: Insufficient Session Expiration

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.