CVE-2017-3857: High severity cisco IOS vulnerability
A vulnerability in the Layer 2 Tunneling Protocol (L2TP) parsing function of Cisco IOS (12.0 through 12.4 and 15.0 through 15.6) and Cisco IOS XE (3.1 through 3.18) could allow an unauthenticated, remote attacker to cause an affected device to reload. The vulnerability is due to insufficient validation of L2TP packets. An attacker could exploit this vulnerability by sending a crafted L2TP packet to an affected device. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a denial of service (DoS) condition. This vulnerability affects Cisco devices that are running a vulnerable release of Cisco IOS or Cisco IOS XE Software if the L2TP feature is enabled for the device and the device is configured as an L2TP Version 2 (L2TPv2) or L2TP Version 3 (L2TPv3) endpoint. By default, the L2TP feature is not enabled. Cisco Bug IDs: CSCuy82078.
Affected Software
Remediation
Recommended actions to resolve this vulnerability, in priority order.
- Configuration
Ensure the L2TP feature is not enabled on the affected device (per statement: by default, the L2TP feature is not enabled). Only devices with L2TP enabled and configured as an L2TPv2 or L2TPv3 endpoint are affected.
Cisco IOS / Cisco IOS XE (L2TP) L2TP feature = not enabled - Compensating control
If L2TP must remain enabled, restrict exposure by allowing L2TP traffic only from trusted sources/management networks (crafted remote L2TP packets can trigger an unauthenticated reload).
Event History
Frequently Asked Questions
What is the severity of CVE-2017-3857?
CVE-2017-3857 has a high severity rating as it allows remote attackers to cause a device to reload.
How do I fix CVE-2017-3857?
To fix CVE-2017-3857, update affected Cisco IOS or IOS XE software to a version that contains the necessary security patches.
Who is affected by CVE-2017-3857?
CVE-2017-3857 affects devices running Cisco IOS versions 12.0 to 12.4 and 15.0 to 15.6, as well as Cisco IOS XE versions 3.1 to 3.18.
What type of vulnerability is CVE-2017-3857?
CVE-2017-3857 is a remote code execution vulnerability related to Layer 2 Tunneling Protocol (L2TP) processing.
Can CVE-2017-3857 be exploited remotely?
Yes, CVE-2017-3857 can be exploited remotely by unauthenticated attackers.