Security readout for executives and security teams
Plain-English summary
This flaw lets a local, authenticated user on affected Mac or Linux VPN endpoints potentially run code as root. It matters most where Cisco AnyConnect has the VPN Posture, HostScan, module installed. There is no source-bundle evidence of active exploitation.
Executive priority
Treat as high priority for managed Mac and Linux VPN fleets, especially shared workstations or developer systems. The business risk is endpoint takeover from an existing local account, not direct remote compromise. Patch planning should follow Cisco guidance because fixed version details are not included in the source bundle.
Technical view
CVE-2021-34788 is a shared library hijacking issue in Cisco AnyConnect Secure Mobility Client for Linux and macOS with HostScan. A race condition in shared library signature verification can let crafted IPC interaction cause root-level arbitrary code execution. CVSS is 7.0, high, with local access and high attack complexity.
Likely exposure
Exposure is limited to Linux and macOS systems running Cisco AnyConnect Secure Mobility Client with the VPN Posture, HostScan, module installed. The attacker also needs a valid local account on the target system. The bundle does not identify affected version ranges.
Exploitation context
The flaw is local privilege escalation, not remote internet exploitation. It requires authenticated local access and high-complexity timing against a race condition. KEV is false, and the provided sources do not state public exploitation in the wild.
Researcher notes
Relevant weakness is CWE-367, time-of-check time-of-use race condition. The security boundary is local authenticated user to root. Validate exposure through product, platform, and HostScan presence; avoid assuming all AnyConnect deployments are affected. No exploit procedure or active exploitation claim is supported by the bundle.
Mitigation direction
- Check Cisco’s advisory for affected and fixed AnyConnect releases.
- Upgrade affected Linux and macOS clients according to Cisco guidance.
- Disable or remove HostScan where it is not operationally required.
- Limit local account access on managed VPN endpoints.
- Prioritize EDR visibility for unexpected root-level process activity.
Validation and detection
- Inventory Linux and macOS endpoints running Cisco AnyConnect.
- Verify whether the VPN Posture, HostScan, module is installed.
- Compare installed client versions with Cisco advisory guidance.
- Confirm unauthorized local accounts are removed or disabled.
- Review endpoint alerts for suspicious privilege escalation behavior.
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-367: 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-2021-34788 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
- 20211006 Cisco AnyConnect Secure Mobility Client for Linux and Mac OS with VPN Posture (HostScan) Module Shared Library Hijacking 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.
Time-of-check Time-of-use (TOCTOU) Race Condition
Time-of-check Time-of-use (TOCTOU) Race Condition represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.