Security readout for executives and security teams
Plain-English summary
Cisco ASA and Firepower Threat Defense devices can be crashed by unauthenticated network traffic processed by the SIP inspection engine. The business impact is availability: affected perimeter or security devices may reload, disrupting protected services and network paths.
Executive priority
Treat as high priority where ASA or FTD devices protect business-critical paths or voice services. It is an availability risk that can interrupt network service, but the bundle does not show active exploitation or compromise of confidentiality.
Technical view
The vulnerability is in SIP inspection handling for a SIP pinhole connection hash lookup. A remote unauthenticated attacker could send crafted SIP traffic through an affected device and trigger a crash and reload. CVSS 3.1 is 8.6 with network attack vector, low complexity, no privileges, and high availability impact.
Likely exposure
Organizations running Cisco ASA Software or Cisco FTD Software where SIP traffic traverses the device are the likely exposure. The supplied bundle does not include exact vulnerable or fixed version ranges.
Exploitation context
The source bundle marks CISA KEV status as false and provides no evidence of active exploitation. Public evidence supports remote unauthenticated denial of service potential, not data theft or code execution.
Researcher notes
Focus validation on SIP inspection exposure and crash/reload telemetry. The bundle lists CWE-613, while the described failure is a crash during hash lookup; confirm weakness mapping and version applicability in Cisco's advisory before reporting scope.
Mitigation direction
- Review the Cisco advisory for affected and fixed release guidance.
- Prioritize upgrades or vendor-recommended mitigations on internet-facing or voice-edge devices.
- Inventory ASA and FTD deployments that inspect or pass SIP traffic.
- Monitor for unexpected ASA or FTD reloads affecting SIP-related traffic paths.
Validation and detection
- Confirm ASA and FTD software versions against Cisco's advisory.
- Identify devices with SIP inspection enabled or SIP traffic traversing them.
- Review device logs for crash, reload, or availability events.
- Verify operational impact for voice, firewall, and remote-access paths.
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-613: 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-2021-1501 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
- 20210428 Cisco Adaptive Security Appliance Software and Cisco Firepower Threat Defense Software SIP 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.
Insufficient Session Expiration
Insufficient Session Expiration represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.