Security readout for executives and security teams
Plain-English summary
CVE-2021-1402 can make an affected Cisco Firepower Threat Defense device reload when it handles certain SSL/TLS traffic under software-based SSL decryption. The business impact is interruption of security gateway availability, not data theft or tampering based on the provided sources.
Executive priority
Treat as high priority where FTD devices sit on critical network paths and perform SSL decryption. The main risk is security gateway downtime and traffic disruption, with automatic recovery after reload according to Cisco.
Technical view
Cisco describes insufficient validation in the software-based SSL/TLS message handler of FTD Software. An unauthenticated remote attacker could cause a process crash and device reload by passing crafted SSL/TLS traffic through an affected device while software-based SSL decryption is active. Traffic sent directly to the device is not the trigger.
Likely exposure
Exposure is most likely on Cisco FTD deployments configured to perform software-based SSL decryption on transit SSL/TLS traffic. FTD devices without that feature path enabled may not be exposed based on the provided description.
Exploitation context
The CVE is not listed as KEV in the supplied bundle, and no cited source states active exploitation. Exploitation would affect availability by causing process crash and reload; the provided sources do not indicate confidentiality or integrity impact.
Researcher notes
The source bundle gives the vulnerable condition and impact, but not affected version ranges or fixed releases. Avoid assuming exploit availability. Validate exposure by configuration and role: the trigger is transit SSL/TLS processing during software-based decryption, not management traffic to the device.
Mitigation direction
- Identify Cisco FTD deployments using software-based SSL decryption policies.
- Review Cisco’s advisory for affected releases and vendor-recommended remediation.
- Prioritize remediation for internet-edge or high-traffic inspection points.
- Monitor FTD reloads and process crashes until remediation is complete.
Validation and detection
- Inventory Cisco FTD versions and SSL decryption policy usage.
- Confirm whether affected devices inspect transit SSL/TLS traffic using software-based decryption.
- Check logs and uptime history for unexpected reloads or related process crashes.
- Track remediation status against Cisco’s advisory, not inferred version assumptions.
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
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Open ATT&CK lookupCVE-2021-1402 mapping review
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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
- 20210428 Cisco Firepower Threat Defense Software SSL Decryption Policy 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 Restriction of Operations within the Bounds of a Memory Buffer
Improper Restriction of Operations within the Bounds of a Memory Buffer represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.