Security readout for executives and security teams
Plain-English summary
This Cisco issue can let a remote, unauthenticated attacker bypass NAT Application Level Gateway handling and open unauthorized connections to a host behind the gateway. It is associated with publicly discussed NAT Slipstreaming behavior. The business risk is moderate because user interaction is required and the CVSS impact is limited to low integrity impact.
Executive priority
Treat as a scheduled security maintenance item, not an emergency, unless critical internal systems depend on exposed NAT ALG behavior. Prioritize confirmation of affected Cisco versions and apply vendor guidance during the next appropriate maintenance window.
Technical view
CVE-2021-34790 covers multiple Cisco ASA and FTD NAT ALG bypass vulnerabilities. The CVSS 3.1 vector is AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N, score 4.7. The source bundle lists ASA affected with versions unspecified, while the description and Cisco advisory title include FTD.
Likely exposure
Exposure is most relevant where Cisco ASA or FTD systems provide NAT ALG handling for traffic to protected internal hosts. Exact affected versions are not included in the source bundle, so teams must confirm release exposure through Cisco guidance.
Exploitation context
The CVE is not listed as KEV in the provided data. The sources describe public discussion as NAT Slipstreaming, but they do not state active exploitation. User interaction is required according to the CVSS vector.
Researcher notes
The public bundle does not provide affected version ranges, fixed releases, or Cisco workaround details. Analysis should stay anchored to Cisco’s advisory and the CVSS requirement for user interaction. Do not infer exploitation from NAT Slipstreaming discussion alone.
Mitigation direction
- Inventory Cisco ASA and FTD deployments using NAT ALG functionality.
- Confirm affected and fixed releases in Cisco’s advisory before changes.
- Apply Cisco-recommended updates or mitigations where applicable.
- Prioritize internet-edge gateways protecting sensitive internal hosts.
Validation and detection
- Compare deployed ASA and FTD versions against Cisco’s advisory.
- Identify NAT ALG usage on affected gateway paths.
- Review logs for unexpected connections to hosts behind ALG protections.
- After remediation, verify gateway policy still blocks unauthorized inbound connections.
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-358: Exact CWE lookup
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Open ATT&CK lookupCVE-2021-34790 mapping review
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Open ATT&CK lookup- Severity
- Medium
- CVSS
- 4.7 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N
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:R/S:C/C:N/I:L/A:N2.81.4Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
4.7MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:N/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- 20211027 Cisco Adaptive Security Appliance Software and Firepower Threat Defense Software Application Level Gateway Bypass VulnerabilitiesCVE 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.
Improperly Implemented Security Check for Standard
Improperly Implemented Security Check for Standard represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.