Cisco Email Security Appliance URL Filtering Bypass Vulnerability
Key facts
- Attack vector
- Network
- Privileges required
- None
- User interaction
- None
- Attack complexity
- Low
- Impact type
- —
- Confidentiality · integrity · availability
- None · Low · None
- Fix status
- No fix listed
Attack profile from CVSS 3.1 · CNA. Fix status from CNA.
Summary
A vulnerability in the antispam protection mechanisms of Cisco AsyncOS Software for Cisco Email Security Appliance (ESA) could allow an unauthenticated, remote attacker to bypass the URL reputation filters on an affected device. This vulnerability is due to improper processing of URLs. An attacker could exploit this vulnerability by crafting a URL in a particular way. A successful exploit could allow the attacker to bypass the URL reputation filters that are configured for an affected device, which could allow malicious URLs to pass through the device.
Why it matters now
SSVC decision points
CISA ADP · SSVC 2.0.3
- Exploitation
- None
- Automatable
- Yes
- Technical impact
- Total
The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.
Affected products
| Vendor | Product | Affected versions | Fixed in | Status | Source |
|---|---|---|---|---|---|
| Cisco | Cisco Email Security Appliance (ESA) | all versions | — | No fix listed | CNA |
- Cisco Email Security Appliance (ESA) VendorCisco Affected all versions Fixed in — No fix listed CNA
CPE configurations NVD · 8
| CPE | Versions | Role | Vendor |
|---|---|---|---|
| cpe:2.3:o:cisco:asyncos:*:*:*:*:*:*:*:* | before 14.0.1 | Vulnerable | Cisco |
| cpe:2.3:h:cisco:email_security_appliance_c170:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:email_security_appliance_c190:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:email_security_appliance_c380:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:email_security_appliance_c390:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:email_security_appliance_c680:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:email_security_appliance_c690:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
| cpe:2.3:h:cisco:email_security_appliance_c690x:-:*:*:*:*:*:*:* | not specified by NVD | Running on | Cisco |
- cpe:2.3:o:cisco:asyncos:*:*:*:*:*:*:*:* Versions before 14.0.1 Vulnerable ·Cisco
- cpe:2.3:h:cisco:email_security_appliance_c170:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:email_security_appliance_c190:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:email_security_appliance_c380:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:email_security_appliance_c390:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:email_security_appliance_c680:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:email_security_appliance_c690:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
- cpe:2.3:h:cisco:email_security_appliance_c690x:-:*:*:*:*:*:*:* Versions not specified by NVD Running on ·Cisco
Remediation
No fixed version listed by the sources yet.
Timeline
- 2026-10-02 Threatist record created from CVE-2021-1534
- 2026-10-03 Alias added: GHSA-86vv-w52w-qq85
References
More Cisco Asyncos vulnerabilities
- TI-2026-74174 Arbitrary file write in Cisco Secure Email Gateway via AMP feature KEVCVSS 3.1CRITICAL 9.8
- TI-2026-53489 Cisco Secure Email Gateway SQL Injection Vulnerability KEVCVSS 3.1CRITICAL 9.8
- TI-2025-14683 Cisco Secure Email Gateway and Cisco Secure Email and Web Manager Remote Command Execution Vulnerability KEVCVSS 3.1CRITICAL 10.0
- TI-2021-13698 Cisco Web Security Appliance Proxy Service Denial of Service Vulnerability CVSS 3.1HIGH 8.6
- TI-2018-11020 Cisco Email Security Appliance URL Filtering Denial of Service Vulnerability CVSS 3.1HIGH 8.6
- TI-2019-01567 Cisco Email Security Appliance Denial of Service Vulnerability CVSS 3.1HIGH 8.6
Sources
- CVE-2021-1534 · CVE Program
- CVE-2021-1534 · NVD
- FIRST EPSS
- GHSA-86vv-w52w-qq85 · GitHub Advisory Database · CC BY 4.0
This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences