Security readout for executives and security teams
Plain-English summary
CVE-2021-34698 can let an unauthenticated remote attacker make a Cisco Web Security Appliance stop accepting new proxy connections by exhausting memory. The business impact is loss of web proxy availability, potentially disrupting user internet access and security filtering. Recovery may require manual intervention.
Executive priority
Treat this as a high-priority availability risk for environments dependent on Cisco WSA for secure web access. It does not indicate data theft, but it can disrupt browsing and security enforcement until the appliance recovers.
Technical view
The flaw is improper memory management in the proxy service of Cisco AsyncOS for Cisco WSA. With network access, an unauthenticated attacker can establish many HTTPS connections, exhausting system memory and causing a denial-of-service condition. CVSS v3.1 is 8.6, availability impact high, with no confidentiality or integrity impact stated.
Likely exposure
Exposure is likely where Cisco Web Security Appliance proxy services are deployed and reachable for HTTPS connection handling. The source bundle does not provide affected AsyncOS version ranges, so teams must verify applicability against Cisco guidance and internal appliance inventory.
Exploitation context
The CVE is not listed as KEV in the provided bundle. The cited description supports unauthenticated remote denial of service, but the bundle does not provide evidence of active exploitation or public exploit availability.
Researcher notes
The source bundle identifies CWE-401 and CVSS AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H. Version-level affected data and concrete fixes are not included in the bundle, so validation should rely on Cisco’s advisory and local asset data.
Mitigation direction
- Check Cisco’s advisory for affected releases, fixed releases, and any vendor-supported workarounds.
- Prioritize remediation for internet-facing or broadly reachable WSA proxy services.
- Limit unnecessary network reachability to the proxy service where operationally feasible.
- Prepare operational recovery procedures because manual intervention may be required after successful exploitation.
Validation and detection
- Inventory Cisco WSA appliances and record AsyncOS versions.
- Compare deployed versions and configuration against Cisco’s advisory.
- Confirm which networks can reach the WSA proxy service over HTTPS.
- Review appliance health, memory, and connection handling logs for unexplained DoS symptoms.
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-401: 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-2021-34698 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 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/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:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H3.94Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
8.6HighVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20211006 Cisco Web Security Appliance Proxy Service 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.
Missing Release of Memory after Effective Lifetime
Missing Release of Memory after Effective Lifetime represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.