CVE-2018-0171

A vulnerability in the Smart Install feature of Cisco IOS Software and Cisco IOS XE Software could allow an unauthenticated, remote attacker to trigger a reload of an affected device, resulting in a denial of service (DoS) condition, or to execute arbitrary code on an affected device. The vulnerability is due to improper validation of packet data. An attacker could exploit this vulnerability by sending a crafted Smart Install message to an affected device on TCP port 4786. A successful exploit could allow the attacker to cause a buffer overflow on the affected device, which could have the following impacts: Triggering a reload of the device, Allowing the attacker to execute arbitrary code on the device, Causing an indefinite loop on the affected device that triggers a watchdog crash. Cisco Bug IDs: CSCvg76186.

CVSS: 9.8Critical
Exploited in the wild: Yes, in CISA KEV since 3 Nov 2021CISA deadline for US federal agencies: 3 May 2022public exploit code
EPSS: 99.5%chance of exploitation in the next 30 daystop 0.1% of scored CVEsFIRST score of 11 Nov 2026
Fix: Patch availablesee the advisories in the references
Published: 28 Mar 2018analysed here 12 Nov 2026

Do first. Apply updates per vendor instructions. (CISA's required action for this KEV entry)

Summary

Triage

Attack surface: Server-side
Exploitable: At runtime
Attack vector: network
Weaknesses: CWE-20 Improper Input Validation
CWE-787 Out-of-Bounds Write
Can a WAF block it?: No. See why

The summary, impact and action text on this page are written by our AI analysis pipeline, or taken from the NVD description when a CVE was imported from NVD. They are not the vendor's wording: check them against the sources. A longer AI executive summary and technical analysis are generated for signed-in accounts on the Max plan.

Affected products

Product	Affected versions	Vendor says fixed in
Cisco IOS and IOS XE	Cisco IOS and IOS XEVendor says fixed in: not stated	Not stated by the vendor

As published in the CVE Program record. A version outside these ranges is not a statement that it is unaffected — vendors sometimes understate a range, and distribution-backported builds carry upstream numbers that do not reflect what was patched into them.

Products named in our analysis

cisco:ios

Fix and mitigation

WAF and other mitigations

Can a WAF block it? No. This is an out-of-bounds write, a memory-corruption bug. Generic WAF rules do not recognise the input that triggers it; only a rule written for this specific CVE can, and only if the triggering request has a recognisable shape.

Also consider: patch

Based on the weakness type only; no CVE-specific evidence yet. We check Cloudflare, AWS, Google Cloud Armor and Azure; for Akamai, Imperva, Fastly, F5, ask your vendor.

Remediation steps (AI-written)

Step-by-step remediation is generated for accounts on the Max plan, for CVEs that match a technology in their stack. Add this technology to your stack to see the fix checklist.

Exploitation evidence

CISA KEV catalog: Listed since 3 Nov 2021.
CISA due date: 3 May 2022, the remediation deadline for US federal agencies
CISA required action: Apply updates per vendor instructions.
Public exploit code: Yes: 1 on Exploit-DB · 1 GitHub proof of concept · 1 Nuclei template
CISA SSVC: exploitation active, automatable yes, technical impact totalAssessed by CISA 8 Nov 2024 (SSVC 2.0.3). Exploitation is none, poc (public proof of concept) or active.

Listed so you can judge urgency, not as a recommendation to run anything. GitHub “proofs of concept” are unvetted: some are fake or carry malware. Exploit-DB marks the entries its staff verified.

Timeline

28 Mar 2018Published
29 Mar 2018First public exploit or proof of conceptsame day later
3 Nov 2021Added to CISA KEV (exploited in the wild)1,315 days (about 4 years) later
3 May 2022CISA remediation due date (US federal agencies)181 days (about 6 months) later
8 Nov 2024CISA SSVC assessment: exploitation active921 days (about 3 years) later
12 Jan 2026CVE record last updated430 days (about 1 year) later
12 Nov 2026Analysed by vulneraibility.com304 days (about 10 months) later

CVSS vector

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

Metric	Value	What it means
Attack vector	NetworkReachable over the internet or any routable network.	Reachable over the internet or any routable network.
Attack complexity	LowRepeatable attack, no special conditions.	Repeatable attack, no special conditions.
Privileges required	NoneThe attacker needs no prior access.	The attacker needs no prior access.
User interaction	NoneNo victim action needed.	No victim action needed.
Scope	UnchangedImpact stays within the vulnerable component.	Impact stays within the vulnerable component.
Confidentiality	HighTotal data disclosure possible.	Total data disclosure possible.
Integrity	HighComplete modification possible.	Complete modification possible.
Availability	HighFull outage possible.	Full outage possible.

Common questions

Is CVE-2018-0171 being exploited?

Yes. CVE-2018-0171 appears in CISA's Known Exploited Vulnerabilities catalog, which means exploitation in the wild has been confirmed and reported. Treat it as active rather than theoretical, and patch it ahead of higher-scoring vulnerabilities that carry no exploitation evidence.

How severe is CVE-2018-0171?

CVE-2018-0171 is rated Critical with a CVSS score of 9.8. Severity describes how bad exploitation would be, not how likely it is: pair it with exploitation evidence before deciding what to patch first.

Is there a patch for CVE-2018-0171?

Yes. A fix has been recorded for CVE-2018-0171. The vendor advisory is the authority on the exact fixed version — apply it from there rather than from a summary.

What does CVE-2018-0171 affect?

CVE-2018-0171 affects cisco:ios. Confirm the exact affected versions against the vendor advisory before deciding you are exposed.

Exploitation status reflects CISA's KEV catalog as we last synced it. Check the catalog directly.

References

NVD CVE.org CVE Details Source

7 references in the CVE record, grouped by the tags the record gives them.

Where the data on this page comes from

CVE List (CVE.org): description, affected versions, references; CVE Terms of Use
NVD: CVSS and CPE data
CISA KEV catalog: exploitation, date added, due date
CISA Vulnrichment (ADP): SSVC decision points
FIRST EPSS: exploit probability and percentile
Exploit-DB: published exploits
Nuclei templates: detection templates
PoC-in-GitHub: GitHub repositories that claim a proof of concept

Summary, impact and triage tags: written by our AI analysis pipeline from the sources above. Check them against the sources.

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