Security readout for executives and security teams
Plain-English summary
Cisco AnyConnect Secure Mobility Client for Windows had flaws in install, uninstall, and upgrade handling. A local authenticated attacker could hijack files used by the client and run code as SYSTEM. This is a serious endpoint privilege-escalation risk, but the provided sources do not show active exploitation.
Executive priority
Treat this as high priority for managed Windows fleets using AnyConnect. It is not remotely exploitable based on the CVSS vector, but SYSTEM-level impact means compromised local accounts could become full endpoint compromise.
Technical view
CVE-2021-1426 covers multiple DLL and executable hijacking vulnerabilities in Cisco AnyConnect Secure Mobility Client for Windows. The attack is local, high complexity, requires low privileges, and needs no user interaction. Successful exploitation can provide SYSTEM-level code execution on the affected Windows device.
Likely exposure
Exposure is most likely on Windows endpoints running Cisco AnyConnect Secure Mobility Client, especially where users can authenticate locally and client install, uninstall, or upgrade workflows occur. The source bundle does not identify exact affected or fixed versions.
Exploitation context
The CVE is not listed as KEV in the provided bundle, so active exploitation is not established here. Exploitation requires valid Windows credentials on the target device and depends on hijacking DLL or executable files during AnyConnect lifecycle operations.
Researcher notes
Key constraints are AV:L, AC:H, PR:L, UI:N, and SYSTEM impact. The source bundle names CWE-378 and describes DLL/executable hijacking during lifecycle processes, but does not provide version ranges, patch versions, or exploit evidence.
Mitigation direction
- Review Cisco advisory cisco-sa-anyconnect-code-exec-jR3tWTA6 for affected and fixed releases.
- Inventory Windows endpoints running Cisco AnyConnect Secure Mobility Client.
- Upgrade or remediate according to Cisco's published guidance.
- Restrict local user privileges where operationally feasible.
- Monitor endpoint software install, uninstall, and upgrade activity.
Validation and detection
- Identify installed AnyConnect versions across Windows endpoint inventory.
- Compare discovered versions against Cisco advisory guidance.
- Check endpoint management logs for recent AnyConnect install, uninstall, or upgrade events.
- Confirm local users do not have unnecessary administrative rights.
- Track remediation status for all AnyConnect Windows clients.
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-2021-1426 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.