Security readout for executives and security teams
Plain-English summary
Cisco Web Security Appliance can be forced into a temporary web proxy outage by malformed HTTP or HTTPS traffic. The impact is availability, not data theft. For businesses relying on WSA for web access control or filtering, this can disrupt user internet access and security enforcement.
Executive priority
Treat as high priority for environments dependent on Cisco WSA for web access, filtering, or policy enforcement. The likely business risk is service disruption rather than compromise, and the provided evidence does not support emergency active-exploitation handling.
Technical view
CVE-2019-1817 is an improper input validation issue in Cisco AsyncOS web proxy functionality for Cisco WSA. An unauthenticated remote attacker can send malformed HTTP or HTTPS requests that restart the web proxy process, causing temporary denial of service. CVSS v3.0 is 8.6, driven by network reachability and high availability impact.
Likely exposure
Exposure is likely limited to organizations running Cisco Web Security Appliance where attackers can send HTTP or HTTPS requests to the proxy. The supplied sources do not identify exact affected versions or deployment-specific exposure conditions.
Exploitation context
The source bundle does not show CISA KEV listing or cited active exploitation. The vulnerability is described as remotely exploitable, but no public exploitation status is supported here.
Researcher notes
The root issue maps to CWE-20: improper input validation. The scope-changing CVSS vector reflects impact beyond the vulnerable component, but the described outcome is web proxy process restart only. Version detail is incomplete in the supplied bundle, so rely on Cisco advisory matching.
Mitigation direction
- Review the Cisco advisory against deployed WSA AsyncOS releases.
- Apply Cisco-recommended fixed software or mitigations where your release is affected.
- Limit who can send HTTP and HTTPS requests to the proxy where feasible.
- Monitor for unexpected web proxy process restarts and availability loss.
Validation and detection
- Inventory Cisco WSA appliances and record AsyncOS versions.
- Confirm each version is addressed by Cisco advisory or later vendor guidance.
- Review monitoring for web proxy restarts or temporary service interruptions.
- Verify proxy access paths are limited to intended networks and users.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-20: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2019-1817 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- High
- CVSS
- 8.6 (3.0)
- Known Exploited
- No
- Published
Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H3.94Primary CVE scoreVulnerability scoring details
Base CVSS 3.0 score
8.6HighVector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20190501 Cisco Web Security Appliance Malformed Request Denial of Service VulnerabilityCVE reference · vendor-advisory, x_refsource_CISCO
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Input Validation
Improper Input Validation represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.