Skip to main content

Time-of-check Time-of-use (TOCTOU) Race Condition

CVE-2021-34788

Severity High
Score 7/10

Summary

A vulnerability in the shared library loading mechanism of Cisco AnyConnect Secure Mobility Client for Linux and Mac OS could allow an authenticated, local attacker to perform a shared library hijacking attack on an affected device if the VPN Posture (HostScan) Module is installed on the AnyConnect client. This vulnerability is due to a race condition in the signature verification process for shared library files that are loaded on an affected device. An attacker could exploit this vulnerability by sending a series of crafted interprocess communication (IPC) messages to the AnyConnect process. A successful exploit could allow the attacker to execute arbitrary code on the affected device with root privileges. To exploit this vulnerability, the attacker must have a valid account on the system.

  • HIGH
  • LOCAL
  • HIGH
  • UNCHANGED
  • NONE
  • LOW
  • HIGH
  • HIGH

CWE-367 - Time-of-check Time-of-use (TOCTOU) Race Condition

The software checks the state of a resource before using that resource, but the resource's state can change between the check and the use in a way that invalidates the results of the check. This can cause the software to perform invalid actions when the resource is in an unexpected state.

References

Advisory Timeline

  • Published