iOSOperating system · Cisco

CVE-2017-12319

MEDIUM · 5.9 CVSS v3.1 Published 2018-03-27

Fix available

A fix is available. Upgrade to 16.3 or later.

See remediation →

100/100

Remediation priority · Urgent

In the wild Remotely reachable No privileges Zero-click

Official description

NVD · unedited

A vulnerability in the Border Gateway Protocol (BGP) over an Ethernet Virtual Private Network (EVPN) for Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause the device to reload, resulting in a denial of service (DoS) condition, or potentially corrupt the BGP routing table, which could result in network instability. The vulnerability exists due to changes in the implementation of the BGP MPLS-Based Ethernet VPN RFC (RFC 7432) draft between IOS XE software releases. When the BGP Inclusive Multicast Ethernet Tag Route or BGP EVPN MAC/IP Advertisement Route update packet is received, it could be possible that the IP address length field is miscalculated. An attacker could exploit this vulnerability by sending a crafted BGP packet to an affected device after the BGP session was established. An exploit could allow the attacker to cause the affected device to reload or corrupt the BGP routing table; either outcome would result in a DoS. The vulnerability may be triggered when the router receives a crafted BGP message from a peer on an existing BGP session. This vulnerability affects all releases of Cisco IOS XE Software prior to software release 16.3 that support BGP EVPN configurations. If the device is not configured for EVPN, it is not vulnerable. Cisco Bug IDs: CSCui67191, CSCvg52875.

Technical summary

dbcve analysis · high confidence

A vulnerability in Cisco IOS XE Software's BGP EVPN implementation allows an unauthenticated remote attacker to cause device reload or corrupt the BGP routing table by sending crafted BGP packets with miscalculated IP address length fields in Inclusive Multicast Ethernet Tag Route or MAC/IP Advertisement Route updates. The vulnerability only affects devices with BGP EVPN configured and exists due to implementation changes in the RFC 7432 draft between software releases.

MitigationUpgrade to Cisco IOS XE Software release 16.3 or later; if upgrade is not immediately possible, verify that BGP EVPN is not configured on affected devices to eliminate the attack vector.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

Affected products & versions

NVD · CPE data

iOSOperating system

Affected:= 15.4$1$s

Ios XeOperating system

Affected:< 16.3

CVSS breakdown

From the vector

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

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

Am I affected?

dbcve checks

Work through these to decide whether this CVE applies to you.

Identify the Cisco IOS XE version

Run 'show version' command and locate the version number in the output (typically displayed as 16.X.Y or similar)

Affected if The version is less than 16.3 (for example, 16.2.x, 16.1.x, or any earlier release)
Verify BGP EVPN is configured

Run 'show running-config | include evpn' or 'show running-config | section router bgp' and look for 'evpn' configuration under the BGP router section

Affected if BGP EVPN is configured and active on the device (presence of 'address-family l2vpn evpn' or 'evpn' commands under router bgp)
Confirm BGP neighbor sessions are established

Run 'show bgp l2vpn evpn summary' to check if any EVPN neighbors are configured and the BGP session is established

Affected if There are active BGP EVPN peers, as the attack vector requires sending crafted packets to these EVPN neighbors

The device is affected only if it runs Cisco IOS XE version below 16.3 AND has BGP EVPN configured with active neighbors, as the vulnerability requires both the vulnerable code path and the feature to be enabled.

Generated from the published advisory. Verify against your own configuration.

Remediation

dbcve · scoped

Upgrade available Upgrade to 16.3 or later

Fixed in 16.3

Interim mitigation

Upgrade to Cisco IOS XE Software release 16.3 or later; if upgrade is not immediately possible, verify that BGP EVPN is not configured on affected devices to eliminate the attack vector.

Recommended fix High confidence

Cisco IOS XE 16.3 or later

Check if the device is configured for BGP EVPN using 'show running-config | include evpn' or 'show ip bgp vpnv4 all' - if not configured for EVPN, the device is not vulnerable
Identify the current Cisco IOS XE Software version using 'show version'
Upgrade Cisco IOS XE Software to version 16.3 or later to remediate this vulnerability
After upgrade, verify BGP EVPN functionality is operational using 'show bgp evpn summary'
Monitor device stability and BGP routing table integrity

Caveat Review Cisco IOS XE 16.3 release notes for any configuration or feature changes that may affect your deployment before upgrading

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in iOS Exploited in the wild — priority engagement

Consultation3.0 h
Implementation6.0 h
Testing4.0 h
Review / QA2.0 h

15.0 hours of engineering $2,640

Get it fixed fast

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Scan for this in your stack

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References

Primary sources

tools.cisco.comVendor Advisory
www.securityfocus.comBroken LinkThird Party AdvisoryVDB Entry
www.cisa.govUS Government Resource
nvd.nist.govNVD record

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2017-12319 in production — separate from our analysis above.

Notes0 Guidelines

Know something about CVE-2017-12319?

The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.

The version that genuinely resolved it — not the one the vendor claimed
A config change or rule that shut the vector down
A gotcha in the upgrade path that cost you an afternoon

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here

Verified mitigations, workarounds, and config changes
Version or environment caveats, and links to real fixes
No weaponised exploit code, or anything meant to cause harm
No spam, self-promotion, credentials, or personal data

At a glance

Exploited in the wildOn CISA’s known-exploited list · agencies must fix by 2022-03-24

A fix existsUpgrade to 16.3 or later

Severity 5.9 Medium

Exploit likelihood EPSS, next 30 days 5.3%

Affects: iOS

Remediation

Being exploited — close it fast

Fix this in iOS 15 hrs · Moderate

Typical engagement from $2,640

Get it fixed fast See the full breakdown ↓

This CVE is on CISA’s actively-exploited list, so the clock is real — a vetted specialist can deliver a reviewed fix for your staging environment quickly.

You’ll deal with our team directly and deploy the reviewed fix to staging first — never straight to production.

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

Check your environment

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

Scan for this in your stack

References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Practitioner notes

No notes yet

Official description

Technical summary

Affected products & versions

CVSS breakdown

Am I affected?

Remediation

References