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Full vulnerability report · 2026
CVE-2026-20084High confidence

Cisco Cisco IOS XE Software: Uncontrolled Resource Consumption

Cisco · Cisco IOS XE Software

Official source article: Cisco CISCO-SA-BOOTP-WUBHNBXA ↗. Check the applicable product and release in the original source.

8.6HighCVSS 3.1
Recommended action
Within 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Fix not verified
R
Operational reassessment

Published severity in operational context

Open reassessment dashboard →
Published severityHighOperational priority:High, unchanged from published severity.unchanged

Evidence used

  • No CISA KEV confirmation is currently recorded.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 0.35% for the current model date.

Compensating controls

  • Restrict the affected network interface to trusted sources where business-safe.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Cisco Cisco IOS XE Software and falls inside the recorded affected range.
  2. Recheck the vendor advisory before scheduling a change because no verified fixed version is currently retained.
  3. Validate exposure, authentication requirements and compensating controls in the actual environment.
  4. Reopen this reassessment when CVSS, KEV, EPSS, exploit evidence or remediation changes.
Mitigation target: Within 30 daysRemediation target: Within 180 days

This automated reassessment organises public evidence. It does not know asset exposure, business impact or control effectiveness and does not replace CVSS or a human risk decision.

Optional official sources

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

Choose official national sources for this report. Each advisory shows its original language. Your selection is remembered on this device and included in shared links.

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-2026-15431

No EUVD known-exploited evidence

ENISA has published the identifier mapping but no EUVD description has been stored yet.

EUVD state
Present in the current official mapping
Known exploitation
Not present in the current ENISA EUVD known-exploited dataset. This is not proof of no exploitation.
ENISA score
Not supplied in the stored EUVD record
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

High technical severity; prioritise exposed affected systems while verifying vendor guidance.

Fix not verified
01

What, why and how

A vulnerability in the DHCP snooping feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause BOOTP packets to be forwarded between VLANs, resulting in a denial of service (DoS) condition. This vulnerability is due to improper handling of BOOTP packets on Cisco Catalyst 9000 Series Switches. An attacker could exploit this vulnerability by sending BOOTP request packets to an affected device. A successful exploit could allow an attacker to forward BOOTP packets from one VLAN to another, resulting in BOOTP VLAN leakage and potentially leading to high CPU utilization. This makes the device unreachable (either through console or remote management) and unable to forward traffic, resulting in a DoS condition. Note: This vulnerability can be exploited with either unicast or broadcast BOOTP packets. There are workarounds that address this vulnerability.

What

A vulnerability in the DHCP snooping feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause BOOTP packets to be forwarded between VLANs, resulting in a denial of service (DoS) condition. This vulnerability is due to improper handling of BOOTP packets on Cisco Catalyst 9000 Series Switches. An attacker could exploit this vulnerability by sending BOOTP request packets to an affected device. A successful exploit could allow an attacker to forward BOOTP packets from one VLAN to another, resulting in BOOTP VLAN leakage and potentially leading to high CPU utilization. This makes the device unreachable (either through console or remote management) and unable to forward traffic, resulting in a DoS condition. Note: This vulnerability can be exploited with either unicast or broadcast BOOTP packets. There are workarounds that address this vulnerability.

Why

The product does not properly control the allocation and maintenance of a limited resource.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

What

A vulnerability in the DHCP snooping feature of Cisco IOS XE Software could allow an unauthenticated, remote attacker to cause BOOTP packets to be forwarded between VLANs, resulting in a denial of service (DoS) condition. This vulnerability is due to improper handling of BOOTP packets on Cisco Catalyst 9000 Series Switches. An attacker could exploit this vulnerability by sending BOOTP request packets to an affected device. A successful exploit could allow an attacker to forward BOOTP packets from one VLAN to another, resulting in BOOTP VLAN leakage and potentially leading to high CPU utilization. This makes the device unreachable (either through console or remote management) and unable to forward traffic, resulting in a DoS condition. Note: This vulnerability can be exploited with either unicast or broadcast BOOTP packets. There are workarounds that address this vulnerability.

Why

The product does not properly control the allocation and maintenance of a limited resource.

How

An attacker operating through a network path may attempt exploitation without authentication or user interaction. If successful, the issue may disrupt the affected service.

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.
No confirmed evidence

No CISA KEV match was present at the last successful refresh. This means no confirmation from that source, not proof of no exploitation.

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 → Uncontrolled Resource Consumption → disrupt the affected service
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-400 ↗

CWE-400: Uncontrolled Resource Consumption. The product does not properly control the allocation and maintenance of a limited resource.

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.
NetworkUnauthenticatedDenial of serviceCWE-400
A

Official authority intelligence

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

BSI · German · WID-SEC-2026-0874Cisco IOS und IOS XE Software: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Cisco IOS XE, Cisco IOS und Cisco Catalyst ausnutzen, um sich erweiterte Rechte zu verschaffen, beliebigen Code auszuführen, Sicherheitsmaßnahmen zu umgehen, Cross-Site-Scripting-Angriffe durchzuführen, Daten zu manipulieren, vertrauliche Informationen offenzulegen und einen Denial-of-Service-Zustand herbeizuführen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20260401Security Bulletin 01 Apr 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 01 Apr 2026, published on 1 April 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-0361Multiples vulnérabilités dans Cisco IOS et IOS XE

De multiples vulnérabilités ont été découvertes dans Cisco IOS et IOS XE. Elles permettent à un attaquant de provoquer un déni de service à distance et un contournement de la politique de sécurité.

Official advisory ↗
JVN iPedia · Japanese · JVNDB-2026-035972シスコシステムズのCisco IOS XEにおけるリソースの枯渇に関する脆弱性

Cisco IOS XE ソフトウェアの DHCP スヌーピング機能に存在する脆弱性により、認証されていないリモート攻撃者が VLAN 間で BOOTP パケットを転送させ、サービス拒否（DoS）状態を引き起こす可能性があります。この脆弱性は、Cisco Catalyst 9000 シリーズスイッチが BOOTP パケットを不適切に処理することに起因しています。攻撃者は影響を受けるデバイスに対して BOOTP リクエストパケットを送信することで、この脆弱性を悪用できます。攻撃が成功すると、攻撃者は BOOTP パケットをある VLAN から別の VLAN に転送させ、BOOTP VLAN の情報漏洩や CPU 使用率の高騰を引き起こす可能性があります。これにより、コンソールまたはリモート管理を通じてデバイスにアクセスできなくなり、トラフィックの転送もできなくなるため、DoS 状態になります。注：この脆弱性は、ユニキャストおよびブロードキャスト BOOTP パケットのいずれでも悪用可能です。この脆弱性に対処するワークアラウンドがあります。

Official advisory ↗
NCSC-NL · Dutch · NCSC-2026-0104Kwetsbaarheden verholpen in Cisco IOS XE Software

A vulnerability in Cisco IOS XE's DHCP snooping feature on Catalyst 9000 Series Switches allows unauthenticated remote attackers to forward BOOTP packets between VLANs, causing VLAN leakage, high CPU usage, and denial of service.

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 XE Software: 16.6.1, 16.6.2, 16.6.3, 16.6.4, 16.6.5, 16.6.4a, 16.6.6, 16.6.7, 16.6.8, 16.6.9, 16.6.10, 16.7.1, 16.8.1, 16.8.1a, 16.8.1s, 16.9.1, 16.9.2, 16.9.1s, 16.9.3, 16.9.4, 16.9.5, 16.9.6, 16.9.7, 16.9.8, 16.10.1, 16.10.1s, 16.10.1e, 16.11.1, 16.11.1b, 16.11.1s, 16.12.1, 16.12.1s, 16.12.1c, 16.12.2, 16.12.3, 16.12.8, 16.12.2s, 16.12.4, 16.12.3s, 16.12.3a, 16.12.4a, 16.12.5, 16.12.6, 16.12.5b, 16.12.6a, 16.12.7, 17.1.1, 17.1.1s, 17.1.1t, 17.1.3, 17.2.1, 17.2.1a, 17.3.1, 17.3.2, 17.3.3, 17.3.2a, 17.3.4, 17.3.5, 17.3.6, 17.3.7, 17.3.8, 17.3.8a, 17.4.1, 17.5.1, 17.6.1, 17.6.2, 17.6.3, 17.6.1y, 17.6.4, 17.6.5, 17.6.6, 17.6.6a, 17.6.5a, 17.6.7, 17.6.8, 17.7.1, 17.10.1, 17.10.1b, 17.8.1, 17.9.1, 17.9.2, 17.9.3, 17.9.4, 17.9.5, 17.9.4a, 17.9.6, 17.9.6a, 17.9.7, 17.9.8, 17.11.1, 17.12.1, 17.12.2, 17.12.3, 17.12.4, 17.12.5, 17.12.1z5, 17.13.1, 17.14.1, 17.15.1, 17.15.2, 17.15.3, 17.15.2b, 17.15.4, 17.15.4d, 17.16.1, 17.17.1, 17.18.1
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.
Official vendor articles1 stored document

Linked articles are downloaded and versioned as source evidence. A CVE mention or approved update relationship does not, by itself, verify a fix for every product branch.

04

Evidence and provenance

Published 25 Mar 2026 · Last source change 26 Mar 2026, 17:35 UTC · CWE-400 · Uncontrolled Resource Consumption

CVE recordCVE.org · 5.2
CVSS sourceCNA
EPSS source
?The date BlackTree first stored a score for this CVE from the daily FIRST EPSS feed.
FIRST · tracked since 2026-08-14
European sourceENISA EUVD · EUVD-2026-15431
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. Vendor guidanceAuthoritative vendor guidance changed: added vendor advisory: sec.cloudapps.cisco.com/cisco-sa-bootp-WuBhNBxA.
    Before
    no authoritative guidance recorded
    After
    vendor advisory: sec.cloudapps.cisco.com/cisco-sa-bootp-WuBhNBxA
    psirt@cisco.com ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    16.6.1; 16.6.2; 16.6.3; 16.6.4; 16.6.5; 16.6.4a; 16.6.6; 16.6.7 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    Cisco IOS XE Software: 16.6.1, 16.6.2, 16.6.3, 16.6.4, 16.6.5, 16.6.4a, 16.6.6, 16.6.7, 16.6.8, 16.6.9, 16.6.10, 16.7.1, 16.8.1, 16.8.1a, 16.8.1s, 16.9.1, 16.9.2, 16.9.1s, 16.9.3, 16.9.4, 16.9.5, 16.9.6, 16.9.7, 16.9.8, 16.10.1, 16.10.1s, 16.10.1e, 16.11.1, 16.11.1b, 16.11.1s, 16.12.1, 16.12.1s, 16.12.1c, 16.12.2, 16.12.3, 16.12.8, 16.12.2s, 16.12.4, 16.12.3s, 16.12.3a, 16.12.4a, 16.12.5, 16.12.6, 16.12.5b, 16.12.6a, 16.12.7, 17.1.1, 17.1.1s, 17.1.1t, 17.1.3, 17.2.1, 17.2.1a, 17.3.1, 17.3.2, 17.3.3, 17.3.2a, 17.3.4, 17.3.5, 17.3.6, 17.3.7, 17.3.8, 17.3.8a, 17.4.1, 17.5.1, 17.6.1, 17.6.2, 17.6.3, 17.6.1y, 17.6.4, 17.6.5, 17.6.6, 17.6.6a, 17.6.5a, 17.6.7, 17.6.8, 17.7.1, 17.10.1, 17.10.1b, 17.8.1, 17.9.1, 17.9.2, 17.9.3, 17.9.4, 17.9.5, 17.9.4a, 17.9.6, 17.9.6a, 17.9.7, 17.9.8, 17.11.1, 17.12.1, 17.12.2, 17.12.3, 17.12.4, 17.12.5, 17.12.1z5, 17.13.1, 17.14.1, 17.15.1, 17.15.2, 17.15.3, 17.15.2b, 17.15.4, 17.15.4d, 17.16.1, 17.17.1, 17.18.1 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
ENISA EUVD · EUVD-2026-15431↗CVE authority or vendor reference · Cisco CISCO-SA-BOOTP-WUBHNBXA↗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-2026-20084 · cve.blacktree.nl