CVE-2023-20227 — A vulnerability in the Layer 2 Tunneling Protocol (L2TP) feature of Cisco IOS XE

A vulnerability in the Layer 2 Tunneling Protocol (L2TP) feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper handling of certain L2TP packets. An

01What is this vulnerability?

A vulnerability in the Layer 2 Tunneling Protocol (L2TP) feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause a denial of service (DoS) condition on an affected device. This vulnerability is due to improper handling of certain L2TP packets. An attacker could exploit this vulnerability by sending crafted L2TP packets to an affected device. A successful exploit…

02Affected products

Vendor	Product	Versions
Cisco	Cisco IOS XE Software	16.8.1, 16.8.1a, 16.8.1b, 16.8.1s, 16.8.1c, 16.8.1d, 16.8.2, 16.8.1e, 16.8.3, 16.9.1, 16.9.2, 16.9.1a, 16.9.1b, 16.9.1s, 16.9.3, 16.9.4, 16.9.5, 16.9.5f, 16.9.6, 16.9.7, 16.9.8, 16.10.1, 16.10.1a, 16.10.1b, 16.10.1s, 16.10.1c, 16.10.1e, 16.10.1d, 16.10.2, 16.10.1f, 16.10.1g, 16.10.3, 16.11.1, 16.11.1a, 16.11.1b, 16.11.2, 16.11.1s, 16.12.1, 16.12.1s, 16.12.1a, 16.12.1c, 16.12.1w, 16.12.2, 16.12.1y, 16.12.2a, 16.12.3, 16.12.8, 16.12.2s, 16.12.1x, 16.12.1t, 16.12.4, 16.12.3s, 16.12.4a, 16.12.5, 16.12.6, 16.12.1z1, 16.12.5a, 16.12.1z2, 16.12.6a, 16.12.7, 16.12.10a, 17.1.1, 17.1.1a, 17.1.1s, 17.1.1t, 17.1.3, 17.2.1, 17.2.1r, 17.2.1a, 17.2.1v, 17.2.2, 17.2.3, 17.3.1, 17.3.2, 17.3.3, 17.3.1a, 17.3.1w, 17.3.2a, 17.3.1x, 17.3.1z, 17.3.4, 17.3.5, 17.3.4a, 17.3.6, 17.3.4c, 17.3.5a, 17.3.5b, 17.3.7, 17.4.1, 17.4.2, 17.4.1a, 17.4.1b, 17.4.2a, 17.5.1, 17.5.1a, 17.5.1b, 17.5.1c

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2023-09-27T17:21:38.623Z
• Last modified: 2024-08-02T09:05:35.876Z

09References

• sec.cloudapps.cisco.com — https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/ci…