QID 317253

Date Published: 2022-11-14

QID 317253: Cisco Internetwork Operating System (IOS) XR Software Bypass Configured First-hop Security (FHS) Vulnerability (cisco-sa-VU855201-J3z8CKTX)

Cisco IOS XR Software running on Layer 2 Transport interfaces handles a VLAN ID 0 tag in accordance with the configurations applied to the device. For port-based services, the packets are forwarded with no inspection.

The affected Cisco IOS XR Software products forward SNAP/LLC frames without additional FHS feature inspection.

Marking this QID as practice as we are not checking "l2transport sub interface configuration"

Affected Products
Cisco IOS XR Software 6.5.3

QID Detection Logic (Authenticated):
The check matches Cisco IOS XR version retrieved via Unix Auth using "show version" command.

Exploitation of these vulnerabilities could allow an adjacent attacker to bypass configured first-hop security (FHS) features on the affected Cisco products.

  • CVSS V3 rated as Medium - 4.7 severity.
  • CVSS V2 rated as Medium - 5 severity.
    • Solution

    Customers are advised to refer to cisco-sa-VU855201-J3z8CKTX for more information.

    Vendor References

    CVEs related to QID 317253

    CVE-2021-27861 |
    Software Advisories
    Advisory ID Software Component Link
    cisco-sa-VU855201-J3z8CKTX URL Logo www.cisco.com/c/en/us/support/docs/csa/cisco-sa-VU855201-J3z8CKTX.html#vp
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