CVE-2017-3857

7.5 HIGH 3% exploit odds No fix listed

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of service disruption.
Exploit odds: 2.6% chance of exploitation in the next 30 days (EPSS).
Fix: No patch or advisory is linked yet. Look at mitigations or restrict exposure.

Timeline

2017-03-22 19:59 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-06-17 01:19 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 2.6% in the next 30 days (EPSS).
Severity: 7.5 HIGH (CVSS).
Fix: none linked yet, which raises it.

Details

Published: 2017-03-22 19:59 UTC
Last modified: 2026-06-17 01:19 UTC
Exploit probability: 2.6% · EPSS, next 30 days
Weakness: CWE-399
Record status: Modified

Affected

Cisco iOS ≤ 12.4
Cisco iOS ≤ 15.6
Cisco iOS Xe ≤ 3.18.0

Attack profile CVSS 3.1 · 7.5

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Raw vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Is it in your code?

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References

NVD record · CVE.org record