Security readout for executives and security teams
Plain-English summary
This flaw lets a logged-in Windows user potentially turn Cisco AnyConnect maintenance activity into SYSTEM-level code execution. It is not a remote internet attack, but it matters because VPN clients are widely deployed and SYSTEM compromise can give deep control over an endpoint.
Executive priority
Address this as a high-severity endpoint privilege escalation. It is less urgent than a remotely exploitable perimeter flaw, but compromised user accounts could use it to deepen endpoint control if vulnerable AnyConnect installations remain unpatched.
Technical view
CVE-2021-1427 covers DLL and executable hijacking in Cisco AnyConnect Secure Mobility Client for Windows install, uninstall, and upgrade processes. The CVSS 3.1 score is 7.0: local attack vector, high complexity, low privileges required, no user interaction, and high confidentiality, integrity, and availability impact.
Likely exposure
Exposure is limited to Windows systems running Cisco AnyConnect Secure Mobility Client. The source bundle does not provide affected version ranges, so teams must compare deployed versions against Cisco's advisory.
Exploitation context
The attacker must already have valid local credentials on the Windows system. The bundle does not show CISA KEV listing or cited evidence of active exploitation, so active exploitation should not be assumed.
Researcher notes
Evidence supports local authenticated privilege escalation through unsafe DLL or executable handling during maintenance operations. The provided bundle identifies CWE-378 and SYSTEM impact, but does not include exact vulnerable versions, exploit maturity, or active exploitation evidence.
Mitigation direction
- Review Cisco's advisory for affected and fixed AnyConnect Windows releases.
- Upgrade vulnerable Cisco AnyConnect Secure Mobility Client installations to vendor-supported fixed versions.
- Prioritize endpoints where AnyConnect upgrades, installs, or removals are performed.
- Limit unnecessary local user access on systems with AnyConnect installed.
- Monitor vendor guidance if exact deployed version status is unclear.
Validation and detection
- Inventory Windows endpoints with Cisco AnyConnect Secure Mobility Client installed.
- Compare installed versions against Cisco's advisory and asset records.
- Check whether affected hosts recently ran install, uninstall, or upgrade workflows.
- Review endpoint telemetry for unusual SYSTEM-level process activity around AnyConnect maintenance.
- Document systems where version evidence is missing or inconclusive.
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-378: 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 lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2021-1427 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
- 7 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/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:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H15.9Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
7HighVector: CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H
Source materials
- CVE List V5 sourceCVE List V5
- 20210505 Cisco AnyConnect Secure Mobility Client for Windows DLL and Executable Hijacking 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.
Creation of Temporary File With Insecure Permissions
Creation of Temporary File With Insecure Permissions represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.