CVE-2021-34749 json
Multiple Cisco Products Server Name Identification Data Exfiltration Vulnerability
published 2021-08-18 5 y ago modified 2026-06-17 4 mo ago also EUVD-2021-21399
- cvss
- 5.8
- 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 77%
- public exploits
- 0
- none known
Summary
A vulnerability in Server Name Identification (SNI) request filtering of Cisco Web Security Appliance (WSA), Cisco Firepower Threat Defense (FTD), and the Snort detection engine could allow an unauthenticated, remote attacker to bypass filtering technology on an affected device and exfiltrate data from a compromised host. This vulnerability is due to inadequate filtering of the SSL handshake. An attacker could exploit this vulnerability by using data from the SSL client hello packet to communicate with an external server. A successful exploit could allow the attacker to execute a command-and-control attack on a compromised host and perform additional data exfiltration attacks.
Patch / fix
CISA SSVC
- Exploitation
- none
- Automatable
- yes
- Technical impact
- partial
- Assessed
- 2 y ago
Exploit prediction
1.68% chance of exploitation in the next 30 days, higher than 77% of all scored CVEs (FIRST EPSS, 2026-11-08).
CVSS scores
| assigned by | version | score | vector |
|---|---|---|---|
| CNA | 3.1 | 5.8 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N |
| NVD | 3.1 | 8.6 | CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:H/A:N |
| NVD | 2.0 | 5.0 | AV:N/AC:L/Au:N/C:N/I:P/A:N |
Affected products
- Cisco Cisco Web Security Appliance (WSA)
Classification
- Weakness
-
- CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
References
-
tools.cisco.com
/security/center/content/CiscoSecurityAdvisory/cisco-sa-sni-data-exfil-mFgzXqLN
vendor-advisory, patch
-
debian.org
/security/2023/dsa-5354
vendor-advisory
-
lists.debian.org
/debian-lts-announce/2023/02/msg00011.html
mailing-list
Sources
- CVE List CVE-2021-34749
- NVD CVE-2021-34749
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