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CVE-2019-1817: Cisco Web Security Appliance Malformed Request Denial of Service Vulnerability

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 1.8% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2019-05-03 · updated 2026-06-17
• Weakness: CWE-20

Description

A vulnerability in the web proxy functionality of Cisco AsyncOS Software for Cisco Web Security Appliance could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. The vulnerability is due to improper validation of HTTP and HTTPS requests. An attacker could exploit this vulnerability by sending a malformed HTTP or HTTPS request to an affected device. An exploit could allow the attacker to cause a restart of the web proxy process, resulting in a temporary DoS condition.

Affected products

• Cisco Web Security Appliance (WSA): 11.5.1-fcs-115, 11.5.1-fcs-124, 11.5.1-fcs-125, 11.7.0-fcs-334

References

• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190501-wsa-dos
• https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20190501-wsa-dos

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