What is CVE-2017-12236?

CVE-2017-12236 is a critical-severity vulnerability in Cisco iOS Xe, classified under Improper Authentication. CVSS score: 9.8/10. Published 2017-09-29.

How severe is CVE-2017-12236?

Critical severity. CVSS v3 base score is 9.8 out of 10.

Auth bypass in Cisco iOS Xe

CVE-2017-12236

A vulnerability in the implementation of the Locator/ID Separation Protocol (LISP) in Cisco IOS XE 3.2 through 16.5 could allow an unauthenticated, remote attacker using an x tunnel router to bypass authentication checks performed when registering an Endpoint Identifier (EID) to a Routing Locator (RLOC) in the map server/map resolver (MS/MR). The vulnerability is due to a logic error introduced via a code regression for the affected software. An attacker could exploit this vulnerability by sending specific valid map-registration requests, which will be accepted by the MS/MR even if the authentication keys do not match, to the affected software. A successful exploit could allow the attacker to inject invalid mappings of EIDs to RLOCs in the MS/MR of the affected software. This vulnerability affects Cisco devices that are configured with LISP acting as an IPv4 or IPv6 map server. This vulnerability affects Cisco IOS XE Software release trains 3.9E and Everest 16.4. Cisco Bug IDs: CSCvc18008.

Vulnerability class: Broken Authentication

Published 2017-09-29 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 9.8 (Critical). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

EPSS exploit prediction

EPSS: 0.031 (87.5th percentile), scored 2026-10-07.

Low probability of exploitation in the next 30 days, but still tracked. 88th percentile — 87.5% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.031 · newest: 0.031 · change: 0.000

Affected products

Cisco iOS Xe — versions 3.2.0ja, 3.9.1e, 16.5.1c
Cisco iOS Xe — versions Cisco IOS XE

Weakness classification (CWE)

CWE-287 — Improper Authentication

References

www.securityfocus.com/bid/101033 (VDB Entry, Third Party Advisory, vdb-entry)
tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20170927… (Vendor Advisory)
www.securitytracker.com/id/1039448 (VDB Entry, Third Party Advisory, vdb-entry)

Frequently asked questions

What is CVE-2017-12236?: CVE-2017-12236 is a critical-severity vulnerability in Cisco iOS Xe, classified under Improper Authentication. CVSS score: 9.8/10. Published 2017-09-29.
How severe is CVE-2017-12236?: Critical severity. CVSS v3 base score is 9.8 out of 10.