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Full vulnerability report · 2018
CVE-2018-0173High confidence

Cisco IOS and IOS XE Software Improper Input Validation Vulnerability

Cisco · IOS and IOS XE Software

8.6HighCVSS 3.1
Recommended action
Protect now

CISA confirms exploitation in the wild and lists 2022-03-17 as the remediation due date.

Fix not verified
Optional official sources

National CERT insights
?CERT means Computer Emergency Response Team; CSIRT is the closely related term Computer Security Incident Response Team.

Select the national-authority views to include. The exact source language is shown on each matched advisory. Your choice is remembered on this device and encoded in the shareable URL.

Official European source

ENISA European Vulnerability Database

Official EUVD identifiers, advisory evidence and known-exploited context. Missing fields are not treated as evidence of low risk.

1 current
ENISA EUVD identifier

EUVD-2018-0996

CISA KEV mirrored by ENISA

A vulnerability in the Cisco IOS Software and Cisco IOS XE Software function that restores encapsulated option 82 information in DHCP Version 4 (DHCPv4) packets could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a Relay Reply denial of service (DoS) condition. The vulnerability exists because the affected software performs incomplete input validation of encapsulated option 82 information that it receives in DHCPOFFER messages from DHCPv4 servers. An attacker could exploit this vulnerability by sending a crafted DHCPv4 packet to an affected device, which the device would then forward to a DHCPv4 server. When the affected software processes the option 82 information that is encapsulated in the response from the server, an error could occur. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. Cisco Bug IDs: CSCvg62754.

EUVD state
Present in the current official mapping
Known exploitation
Recorded by ENISA since 3 Mar 2022. Evidence sources: cisa_kev.
ENISA score
8.6 · CVSS 3.1
Advisory evidence
3 linked advisory records
Recommended actionProtect now

CISA confirms exploitation in the wild and lists 2022-03-17 as the remediation due date.

Fix not verified
01

What, why and how

A vulnerability in the Cisco IOS Software and Cisco IOS XE Software function that restores encapsulated option 82 information in DHCP Version 4 (DHCPv4) packets can allow for denial-of-service (DoS).

What

A vulnerability in the Cisco IOS Software and Cisco IOS XE Software function that restores encapsulated option 82 information in DHCP Version 4 (DHCPv4) packets can allow for denial-of-service (DoS).

Why

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

What

A vulnerability in the Cisco IOS Software and Cisco IOS XE Software function that restores encapsulated option 82 information in DHCP Version 4 (DHCPv4) packets can allow for denial-of-service (DoS).

Why

The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may cause the confidentiality, integrity or availability impact described by the vendor.

02

Exploit reality and attack path

CVSS severity, EPSS forecast probability, public exploit material and CISA-confirmed exploitation are separate signals.

Observed exploitation
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
Confirmed in the wild

CISA added this CVE to its Known Exploited Vulnerabilities catalogue on 2022-03-03.

Public PoC / exploit material
?Confirmed exploitation and public exploit material are separate signals. Attacks can occur without public proof-of-concept or exploit code.
None recorded

No exploit-tagged reference or CISA SSVC proof-of-concept state is currently recorded. Research may still exist outside the structured feeds.

Likely attack path
a network path → Improper Input Validation → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Network
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
Low: no specialised conditions are recorded
Security boundary
Changed: exploitation can affect a different security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-20 ↗

CWE-20: Improper Input Validation. The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H

Common Vulnerability Scoring System 3.1: the compact vector below is decoded into plain language.

AVNetworkAttack vector: The vulnerable component can be reached over a network.ACLowAttack complexity: No specialised conditions are required beyond attacker-controlled input.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.SChangedScope: The attack can affect a component governed by a different security authority.CNoneConfidentiality impact: No direct loss is represented by this metric.INoneIntegrity impact: No direct loss is represented by this metric.AHighAvailability impact: A successful attack can cause a major loss.
Post-exploitation / living off the land
No specific living-off-the-land technique is confirmed in the structured sources. Monitor normal administration tools for activity inconsistent with the affected service's baseline.
NetworkUnauthenticatedCWE-20CISA KEV
A

Official authority intelligence

Only matched European and national findings are included. Language selectors and unavailable sources are omitted.

ENISA EUVD · EUVD-2018-0996Known-exploited evidence recorded

A vulnerability in the Cisco IOS Software and Cisco IOS XE Software function that restores encapsulated option 82 information in DHCP Version 4 (DHCPv4) packets could allow an unauthenticated, remote attacker to cause an affected device to reload, resulting in a Relay Reply denial of service (DoS) condition. The vulnerability exists because the affected software performs incomplete input validation of encapsulated option 82 information that it receives in DHCPOFFER messages from DHCPv4 servers. An attacker could exploit this vulnerability by sending a crafted DHCPv4 packet to an affected device, which the device would then forward to a DHCPv4 server. When the affected software processes the option 82 information that is encapsulated in the response from the server, an error could occur. A successful exploit could allow the attacker to cause the affected device to reload, resulting in a DoS condition. Cisco Bug IDs: CSCvg62754.

Official EUVD record ↗
BSI · German · WID-SEC-2025-1871Cisco IOS: Mehrere Schwachstellen

Ein entfernter, anonymer oder authentisierter Angreifer kann mehrere Schwachstellen in Cisco IOS und Cisco IOS XE ausnutzen, um Daten zu manipulieren, vertrauliche Daten einzusehen, einen Denial of Service Angriff durchzuführen, seine Privilegien zu erweitern, Cross-Site Scripting Angriffe durchzuführen, Sicherheitsmechanismen zu umgehen oder beliebigen Code mit administrativen Privilegien zur Ausführung zu bringen.

Official advisory ↗
Canadian Centre for Cyber Security · English · AV18-052Cisco security updates

Shell Access Vulnerability -Cisco IOS XE Software Privileged EXEC Mode Root Shell Access Vulnerability -Cisco IOS Software 802.1x Multiple-Authentication Port Authentication Bypass Vulnerability -Cisco IOS XE Software CLI Command Injection Vulnerabilities -Cisco IOS and IOS XE Software Forwarding Information Base Denial of Service Vulnerability CVE References:  CVE-2018-0150, CVE-2018-0151, CVE-2018-0152, CVE-2018-0154, CVE-2018-0155, CVE-2018-0156, CVE-2018-0157, CVE-2018-0158, CVE-2018-0159, CVE-2018-0160, CVE-2018-0161, CVE-2018-0163, CVE-2018-0164, CVE-2018-0165, CVE-2018-0167, CVE-2018-0169, CVE-2018-0170, CVE-2018-0171, CVE-2018-0172, CVE-2018-0173, CVE-2018-0174, CVE-2018-0175, CVE-2018-0176, CVE-2018-0177, CVE-2018-0179, CVE-2018-0180, CVE-2018-0182, CVE-2018-0183, CVE-2018-0184, CVE-2018-0185, CVE-2018-0186, CVE-2018-0188, CVE-2018-0189, CVE-2018-0190, CVE-2018-0193, CVE-2018-0195, CVE-2018-0196 Suggested Action CCIRC recommends that system administrators test and deploy the vendor-released updates to affected applications accordingly. References: https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-xesc https://tools.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-20180328-smi2 https://tools.cisco.com/security/center/content/Cisco

Official advisory ↗
CERT-FR · French · CERTFR-2018-AVI-156Multiples vulnérabilités dans les produits Cisco

.cve.org/CVERecord?id=CVE-2018-0159 Référence CVE CVE-2018-0160 https://www.cve.org/CVERecord?id=CVE-2018-0160 Référence CVE CVE-2018-0161 https://www.cve.org/CVERecord?id=CVE-2018-0161 Référence CVE CVE-2018-0165 https://www.cve.org/CVERecord?id=CVE-2018-0165 Référence CVE CVE-2018-0167 https://www.cve.org/CVERecord?id=CVE-2018-0167 Référence CVE CVE-2018-0169 https://www.cve.org/CVERecord?id=CVE-2018-0169 Référence CVE CVE-2018-0170 https://www.cve.org/CVERecord?id=CVE-2018-0170 Référence CVE CVE-2018-0171 https://www.cve.org/CVERecord?id=CVE-2018-0171 Référence CVE CVE-2018-0172 https://www.cve.org/CVERecord?id=CVE-2018-0172 Référence CVE CVE-2018-0173 https://www.cve.org/CVERecord?id=CVE-2018-0173 Référence CVE CVE-2018-0174 https://www.cve.org/CVERecord?id=CVE-2018-0174 Référence CVE CVE-2018-0175 https://www.cve.org/CVERecord?id=CVE-2018-0175 Référence CVE CVE-2018-0176 https://www.cve.org/CVERecord?id=CVE-2018-0176 Référence CVE CVE-2018-0177 https://www.cve.org/CVERecord?id=CVE-2018-0177 Gestion détaillée du document le 29 mars 2018 Version initiale Alertes Avis Bulletins d’actualités Mentions légales Conditions générales À propos Contact cyber.gouv.fr service-public.fr legifrance.gouv.fr info.gouv.fr france.fr info.gouv.fr/risques Premier Ministre / Secrétariat Général de la Défense

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2018-003507Cisco IOS ソフトウェアおよび Cisco IOS XE ソフトウェアにおける入力確認に関する脆弱性

Cisco IOS ソフトウェアおよび Cisco IOS XE ソフトウェアには、入力確認に関する脆弱性が存在します。 ベンダは、本脆弱性を Bug ID CSCvg62754 として公開しています。

Official advisory ↗
KISA KrCERT/CC · Korean · KNVD-4847Cisco IOS 소프트웨어 신규 취약점 보안 업데이트 권고

Cisco IOS 및 XE 소프트웨어의 DHCP 버전 4의 역캡슐화 기능에서 발생하는 서비스 거부 취약점(CVE-2018-0173) [18]

Official advisory ↗
03

Patch and workaround

Operational remediation based on structured source evidence.

Status
?Patch availability is based on structured fixed-version fields and authoritative update references. If no fix is verified, check the vendor advisory before making a change.
Fix not verified
Affected
Cisco IOS and IOS XE: Cisco IOS and IOS XE
Fixed
No fixed version is explicitly recorded in the structured CVE data.
Action
No verified patch reference is present in the current structured sources. Check the vendor advisory before making a change.
Workaround
No verified workaround is recorded. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 28 Mar 2018 · Last source change 12 Jan 2026, 22:00 UTC · CWE-20 · Improper Input Validation

CVE recordCVE.org · 5.2
CVSS sourceNIST NVD
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-09-01
European sourceENISA EUVD · EUVD-2018-0996
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD enriched

Core structured fields are present and their contributing authorities are shown above.

Material change intelligence

What changed after publication

View recent updates ↗
  1. Affected versionsThe structured affected or fixed version information changed.
    Before
    Cisco IOS and IOS XE · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    Cisco IOS and IOS XE: Cisco IOS and IOS XE · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
  2. Vendor guidanceAuthoritative vendor guidance changed from no authoritative guidance recorded to vendor advisory.
    Before
    no authoritative guidance recorded
    After
    vendor advisory
    af854a3a-2127-422b-91ae-364da2661108 ↗
  3. CVSS scoreCVSS scoring authority changed from CISA ADP to NIST NVD; the displayed base score remained 8.6.
    Before
    8.6 (CVSS 3.1 · CISA ADP · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H)
    After
    8.6 (CVSS 3.1 · NIST NVD · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:H)
    NIST NVD ↗
  4. ENISA known-exploited stateENISA EUVD now records this CVE in its known-exploited dataset.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2018-0996","listed":true,"sources":["cisa_kev"]}
    ENISA EUVD ↗
  5. ENISA EUVD mappingEUVD-2018-0996 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2018-0996"}
    ENISA EUVD ↗
  6. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Added to CISA KEV
ENISA EUVD · EUVD-2018-0996↗CISA KEV record↗CVE authority or vendor reference↗Official CVE record (CNA and ADP data)↗NVD record↗
Technical terms and abbreviations used in this report
CVE
Common Vulnerabilities and Exposures: the public identifier for one disclosed vulnerability.
CVSS
Common Vulnerability Scoring System: a technical severity framework; it is not patching priority by itself.
EPSS
Exploit Prediction Scoring System: FIRST's estimate of the probability that exploitation activity will be observed in the next 30 days; it is a forecast, not confirmation.
CWE
Common Weakness Enumeration: the standard category describing the underlying software or hardware weakness.
CNA
CVE Numbering Authority: an organisation authorised to assign and publish CVE records.
CISA ADP
Cybersecurity and Infrastructure Security Agency Authorized Data Publisher: structured enrichment added to a CVE record.
NVD
National Vulnerability Database: NIST's enrichment service for CVE records.
CERT / CSIRT
A computer security incident response team that publishes warnings or coordinates incident response.
PoC
Proof of concept: public material that demonstrates or helps reproduce exploitation.
CSAF
Common Security Advisory Framework: a machine-readable format for security advisories.
LoTL
Living off the land: abuse of legitimate tools or system functions during an attack.
Free version - for non-commercial use only.CVE-2018-0173 · cve.blacktree.nl