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Full vulnerability report · 2026
CVE-2026-78011High confidence

Fireware OS Integer Underflow in Iked Allows Unauthenticated Denial of Service (DoS)

WatchGuard · Fireware OS

8.7HighCVSS 4.0
Recommended action
Within 7 days

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

Patch available
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 0.54% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • 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 WatchGuard Fireware OS and falls inside the recorded affected range.
  2. Verify the installed build against the product-specific fixed version after deployment.
  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-2026-67336

No EUVD known-exploited evidence

An integer underflow vulnerability in the WatchGuard Fireware OS iked process allows a remote unauthenticated attacker to create a Denial of Service (DoS) condition in VPN processing by sending specially crafted network traffic.

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
8.7 · CVSS 4.0
Advisory evidence
No linked advisory details stored yet
Recommended actionWithin 7 days

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

Patch available
01

What, why and how

An integer underflow vulnerability in the WatchGuard Fireware OS iked process allows a remote unauthenticated attacker to create a Denial of Service (DoS) condition in VPN processing by sending specially crafted network traffic.

What

An integer underflow vulnerability in the WatchGuard Fireware OS iked process allows a remote unauthenticated attacker to create a Denial of Service (DoS) condition in VPN processing by sending specially crafted network traffic.

Why

The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

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

An integer underflow vulnerability in the WatchGuard Fireware OS iked process allows a remote unauthenticated attacker to create a Denial of Service (DoS) condition in VPN processing by sending specially crafted network traffic.

Why

The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

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 → Integer Underflow (Wrap or Wraparound) → 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
Not a CVSS 4.0 base metric
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-191 ↗

CWE-191: Integer Underflow (Wrap or Wraparound). The product subtracts one value from another, such that the result is less than the minimum allowable integer value, which produces a value that is not equal to the correct result.

CVSS vector
?CVSS means Common Vulnerability Scoring System. The vector records the metric values used to calculate technical severity.
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N

Common Vulnerability Scoring System 4.0: 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.ATNoneAttack requirements: No additional deployment or execution condition is required.PRNonePrivileges required: The attacker does not need an account or existing privileges.UINoneUser interaction: No action by another user is required.VCNoneVulnerable-system confidentiality: No direct loss is represented by this metric.VINoneVulnerable-system integrity: No direct loss is represented by this metric.VAHighVulnerable-system availability: A successful attack can cause a major loss.SCNoneSubsequent-system confidentiality: No direct loss is represented by this metric.SINoneSubsequent-system integrity: No direct loss is represented by this metric.SANoneSubsequent-system availability: No direct loss is represented by this metric.
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-191
A

Official authority intelligence

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

ENISA EUVD · EUVD-2026-67336Official EUVD mapping

An integer underflow vulnerability in the WatchGuard Fireware OS iked process allows a remote unauthenticated attacker to create a Denial of Service (DoS) condition in VPN processing by sending specially crafted network traffic.

Official EUVD record ↗
BSI · German · WID-SEC-2026-3068WatchGuard Firebox OS: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in WatchGuard Firebox OS ausnutzen, um beliebigen Code – einschließlich Code mit Root-Rechten – auszuführen oder einen Denial-of-Service-Zustand herbeizuführen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20260902Security Bulletin 2 Sept 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 2 Sept 2026, published on 2 September 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CSIRT Italia · Italian · risolte-vulnerabilita-in-prodotti-watchguard-1Risolte vulnerabilità in prodotti WatchGuard

Aggiornamenti di sicurezza sanano numerose vulnerabilità, tra cui 5 con gravità "critica" e 12 con gravità “alta”, in prodotti WatchGuard. Tali vulnerabilità, qualora sfruttate, potrebbero consentire a un utente malintenzionato di eludere i meccanismi di autenticazione, eseguire codice arbitrario e/o compromettere la disponibilità del servizio sui sistemi interessati.

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.
Patch available
Affected
Fireware OS: 12.0 < 12.12.2, 2025.0 < 2026.2.2, 12.0 < 12.5.20, 2026.3 < 2026.3.1
Fixed
Fireware OS 2026.3.1, Fireware OS 2026.2.2, Fireware OS 12.12.2, Fireware OS 12.5.20
Action
Review the linked authoritative reference and apply the recorded fixed release appropriate to the affected product branch.
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 27 Aug 2026 · Last source change 3 Sept 2026, 20:49 UTC · CWE-191 · Integer Underflow (Wrap or Wraparound)

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 2026-08-28
European sourceENISA EUVD · EUVD-2026-67336
Product sourceCNA
Remediation sourceCVE/CNA references
CWE sourceCNA
NVD statusNVD not scheduled

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
    Fireware OS: 2025.0 < 2026.2.2, 12.0 < 12.12.2, 12.0 < 12.5.20 · Fixed: Fireware OS 2026.2.2, Fireware OS 12.12.2, Fireware OS 12.5.20
    After
    Fireware OS: 2025.0 < 2026.2.2, 12.0 < 12.12.2, 2026.3 < 2026.3.1, 12.0 < 12.5.20 · Fixed: Fireware OS 2026.3.1, Fireware OS 2026.2.2, Fireware OS 12.12.2, Fireware OS 12.5.20
    CNA ↗
  2. Affected versionsThe structured affected or fixed version information changed.
    Before
    2025.0 < 2026.2.2; 12.0 < 12.12.2; 12.0 < 12.5.20 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    2025.0 < 2026.2.2; 12.0 < 12.12.2; 2026.3 < 2026.3.1; 12.0 < 12.5.20 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    CNA ↗
  3. BlackTree coverageBlackTree article coverage changed from no BlackTree article to 1 BlackTree article.
    Before
    no BlackTree article
    After
    1 BlackTree article
    BlackTree editorial ↗
  4. Vendor guidanceAuthoritative vendor guidance changed: added remediation: psirt.watchguard.com/CVE-2026-78011.
    Before
    no authoritative guidance recorded
    After
    remediation: psirt.watchguard.com/CVE-2026-78011
    CNA ↗
  5. Affected versionsThe structured affected or fixed version information changed.
    Before
    2025.0 < 2026.2.2; 12.0 < 12.12.2; 2026.3 < 2026.3.1; 12.0 < 12.5.20 · Fixed: No fixed version is explicitly recorded in the structured CVE data.
    After
    Fireware OS: 2025.0 < 2026.2.2, 12.0 < 12.12.2, 12.0 < 12.5.20 · Fixed: Fireware OS 2026.2.2, Fireware OS 12.12.2, Fireware OS 12.5.20
    CNA ↗
  6. Remediation statusRemediation status changed from Awaiting fix to Patch available.
    Before
    Awaiting fix
    After
    Patch available
    CNA ↗
  7. ENISA EUVD mappingEUVD-2026-67336 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-67336"}
    ENISA EUVD ↗
  8. Vendor guidanceAuthoritative vendor guidance changed: removed vendor advisory: psirt.watchguard.com/CVE-2026-78011.
    Before
    vendor advisory: psirt.watchguard.com/CVE-2026-78011
    After
    no authoritative guidance recorded
    CNA ↗
  9. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Fixed release or patch reference recorded
ENISA EUVD · EUVD-2026-67336↗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-2026-78011 · cve.blacktree.nl