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Full vulnerability report · 2026
CVE-2026-20323High confidence

Cisco Secure Firewall Management Center and Secure Firewall Threat Defense Software sftunnel Unauthorized Authentication Bypass Vulnerability

Cisco · Cisco Secure Firewall Management Center (FMC)

Official source article: Cisco CISCO-SA-FMCFTD-SFTUN-MULTIVULNS-WGVHORN3 ↗. Check the applicable product and release in the original source.

8.3HighCVSS 3.1
Recommended action
Patch only the product branches with a verified fix

High technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 368 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
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.
  • EPSS is 0.09% for the current model date.

Compensating controls

  • Validate the affected product branch and deploy the verified fixed release.
  • Restrict local access and enforce least privilege on affected hosts.
  • Monitor vendor guidance and exploitation sources for a material change.

Verification

  1. Confirm that the asset runs Cisco Cisco Secure Firewall Management Center (FMC) 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.

Cross-source reconciliation

Remediation availability differs by product scope

Verified remediation exists for at least one product or source, but 368 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Direct vendor intelligence

Authoritative vendor CSAF and VEX advisories

Structured product status and remediation from the issuing vendor. Product-state explanations are always visible; large lists can be searched or downloaded.

1 current
cisco-sa-fmcftd-sftun-multivulns-WGVHOrN3 · CSAF 2.0 · revision 1.0.0 · finalCisco PSIRTCisco Secure Firewall Management Center and Secure Firewall Threat Defense Software sftunnel Unauthorized Authentication Bypass Vulnerability
368 known affected

The vendor explicitly identifies these products as affected by this CVE.

  • Cisco Secure Firewall Management Center (FMC) 7.2.0 when installed on Cisco Secure Firewall Management Center (FMC) Appliances
  • Cisco Secure Firewall Management Center (FMC) 7.2.1 when installed on Cisco Secure Firewall Management Center (FMC) Appliances
  • Cisco Secure Firewall Management Center (FMC) 7.3.0 when installed on Cisco Secure Firewall Management Center (FMC) Appliances
  • Cisco Secure Firewall Management Center (FMC) 7.2.2 when installed on Cisco Secure Firewall Management Center (FMC) Appliances
  • Cisco Secure Firewall Management Center (FMC) 7.2.0.1 when installed on Cisco Secure Firewall Management Center (FMC) Appliances
  • Cisco Secure Firewall Management Center (FMC) 7.2.3 when installed on Cisco Secure Firewall Management Center (FMC) Appliances
  • Cisco Secure Firewall Management Center (FMC) 7.3.1 when installed on Cisco Secure Firewall Management Center (FMC) Appliances
  • Cisco Secure Firewall Management Center (FMC) 7.2.3.1 when installed on Cisco Secure Firewall Management Center (FMC) Appliances
  • Cisco Secure Firewall Management Center (FMC) 7.2.4 when installed on Cisco Secure Firewall Management Center (FMC) Appliances
  • Cisco Secure Firewall Management Center (FMC) 7.2.4.1 when installed on Cisco Secure Firewall Management Center (FMC) Appliances
  • Cisco Secure Firewall Management Center (FMC) 7.2.5 when installed on Cisco Secure Firewall Management Center (FMC) Appliances
  • Cisco Secure Firewall Management Center (FMC) 7.3.1.1 when installed on Cisco Secure Firewall Management Center (FMC) Appliances
Summary
Complete.
Remediation
Cisco has released software updates that address this vulnerability.
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-2026-81139

No EUVD known-exploited evidence

A vulnerability in the sftunnel inter-device communication protocol of Cisco Secure FMC Software and Cisco Secure FTD Software could allow an unauthenticated, adjacent attacker to impersonate the peer device and obtain access at the level of the manager role, which is equivalent to root. This vulnerability is due to improper management of the TLS certificate for the sftunnel management connection. An attacker could exploit this vulnerability by connecting to the sftunnel port using a crafted TLS certificate. A successful exploit could allow the attacker to become a registered sftunnel peer with root access. Note: The attack is successful only if the sftunnel connection is down or the attack can disrupt the sftunnel connection long enough to execute the attack.

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
8.3 · CVSS 3.1
Advisory evidence
No linked advisory details stored yet
Recommended actionPatch only the product branches with a verified fix

High technical severity; prioritise exposed affected systems while verifying vendor guidance. Verified remediation exists for at least one product or source, but 368 structured product or package states remain unresolved. Apply remediation only to the exact product branch confirmed by its source.

Fix availability varies by product
01

What, why and how

A vulnerability in the sftunnel inter-device communication protocol of Cisco Secure FMC Software and Cisco Secure FTD Software could allow an unauthenticated, adjacent attacker to impersonate the peer device and obtain access at the level of the manager role, which is equivalent to root. This vulnerability is due to improper management of the TLS certificate for the sftunnel management connection. An attacker could exploit this vulnerability by connecting to the sftunnel port using a crafted TLS certificate. A successful exploit could allow the attacker to become a registered sftunnel peer with root access. Note: The attack is successful only if the sftunnel connection is down or the attack can disrupt the sftunnel connection long enough to execute the attack.

What

A vulnerability in the sftunnel inter-device communication protocol of Cisco Secure FMC Software and Cisco Secure FTD Software could allow an unauthenticated, adjacent attacker to impersonate the peer device and obtain access at the level of the manager role, which is equivalent to root. This vulnerability is due to improper management of the TLS certificate for the sftunnel management connection. An attacker could exploit this vulnerability by connecting to the sftunnel port using a crafted TLS certificate. A successful exploit could allow the attacker to become a registered sftunnel peer with root access. Note: The attack is successful only if the sftunnel connection is down or the attack can disrupt the sftunnel connection long enough to execute the attack.

Why

The product does not validate, or incorrectly validates, a certificate.

How

An attacker operating through an adjacent network 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 sftunnel inter-device communication protocol of Cisco Secure FMC Software and Cisco Secure FTD Software could allow an unauthenticated, adjacent attacker to impersonate the peer device and obtain access at the level of the manager role, which is equivalent to root. This vulnerability is due to improper management of the TLS certificate for the sftunnel management connection. An attacker could exploit this vulnerability by connecting to the sftunnel port using a crafted TLS certificate. A successful exploit could allow the attacker to become a registered sftunnel peer with root access. Note: The attack is successful only if the sftunnel connection is down or the attack can disrupt the sftunnel connection long enough to execute the attack.

Why

The product does not validate, or incorrectly validates, a certificate.

How

An attacker operating through an adjacent network 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.
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
an adjacent network → Improper Certificate Validation → cause the confidentiality, integrity or availability impact described by the vendor
Attack surface
Adjacent
Privileges required
None: unauthenticated exploitation is possible
User interaction
None
Attack complexity
High: exploitation depends on specific conditions
Security boundary
Changed: exploitation can affect a different security authority
Weakness
?CWE means Common Weakness Enumeration: a standard category for the underlying weakness.
CWE-295 ↗

CWE-295: Improper Certificate Validation. The product does not validate, or incorrectly validates, a certificate.

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

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

AVAdjacentAttack vector: The attacker must be on an adjacent or logically close network.ACHighAttack complexity: Successful exploitation depends on specific conditions outside the attacker's direct control.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.CHighConfidentiality impact: A successful attack can cause a major loss.IHighIntegrity impact: A successful attack can cause a major loss.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.
UnauthenticatedCWE-295
A

Official authority intelligence

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

ENISA EUVD · EUVD-2026-81139Official EUVD mapping

A vulnerability in the sftunnel inter-device communication protocol of Cisco Secure FMC Software and Cisco Secure FTD Software could allow an unauthenticated, adjacent attacker to impersonate the peer device and obtain access at the level of the manager role, which is equivalent to root. This vulnerability is due to improper management of the TLS certificate for the sftunnel management connection. An attacker could exploit this vulnerability by connecting to the sftunnel port using a crafted TLS certificate. A successful exploit could allow the attacker to become a registered sftunnel peer with root access. Note: The attack is successful only if the sftunnel connection is down or the attack can disrupt the sftunnel connection long enough to execute the attack.

Official EUVD record ↗
BSI · German · WID-SEC-2026-3423Cisco Secure Firewall Threat Defense: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Cisco Secure Firewall Threat Defense ausnutzen, um einen Denial of Service Angriff durchzuführen, um Sicherheitsvorkehrungen zu umgehen, und um seine Privilegien zu erhöhen.

Official advisory ↗
BSI · German · WID-SEC-2026-3417Cisco Secure Firewall Management Center: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Cisco Secure Firewall Management Center ausnutzen, um Sicherheitsmaßnahmen zu umgehen, beliebige Befehle als Root auszuführen, Berechtigungen auf Root zu erweitern, SQL-Injection durchzuführen, Anmeldedaten für Administratorsitzungen zu erlangen, sensible Daten zu manipulieren und offenzulegen oder Denial-of-Service-Zustände herbeizuführen.

Official advisory ↗
Cyber Security Agency of Singapore · English · CSA-SB-20260923Security Bulletin 23 Sep 2026

The Cyber Security Agency of Singapore included this CVE in its official Security Bulletin 23 Sep 2026, published on 23 September 2026. Open the linked bulletin for the product, severity and reference information published in that issue.

Official advisory ↗
CERT-FR · French · CERTFR-2026-AVI-1197Multiples vulnérabilités dans les produits Cisco

d?id=CVE-2026-20283 Référence CVE CVE-2026-20284 https://www.cve.org/CVERecord?id=CVE-2026-20284 Référence CVE CVE-2026-20287 https://www.cve.org/CVERecord?id=CVE-2026-20287 Référence CVE CVE-2026-20295 https://www.cve.org/CVERecord?id=CVE-2026-20295 Référence CVE CVE-2026-20300 https://www.cve.org/CVERecord?id=CVE-2026-20300 Référence CVE CVE-2026-20305 https://www.cve.org/CVERecord?id=CVE-2026-20305 Référence CVE CVE-2026-20306 https://www.cve.org/CVERecord?id=CVE-2026-20306 Référence CVE CVE-2026-20307 https://www.cve.org/CVERecord?id=CVE-2026-20307 Référence CVE CVE-2026-20322 https://www.cve.org/CVERecord?id=CVE-2026-20322 Référence CVE CVE-2026-20323 https://www.cve.org/CVERecord?id=CVE-2026-20323 Référence CVE CVE-2026-20324 https://www.cve.org/CVERecord?id=CVE-2026-20324 Référence CVE CVE-2026-20325 https://www.cve.org/CVERecord?id=CVE-2026-20325 Référence CVE CVE-2026-20326 https://www.cve.org/CVERecord?id=CVE-2026-20326 Référence CVE CVE-2026-20329 https://www.cve.org/CVERecord?id=CVE-2026-20329 Référence CVE CVE-2026-20330 https://www.cve.org/CVERecord?id=CVE-2026-20330 Référence CVE CVE-2026-20331 https://www.cve.org/CVERecord?id=CVE-2026-20331 Référence CVE CVE-2026-20332 https://www.cve.org/CVERecord?id=CVE-2026-20332 Référence CVE CVE-2026-20333 https://www.cve.org/CVERecord?id=

Official advisory ↗
CSIRT Italia · Italian · risolte-vulnerabilita-in-prodotti-cisco-32Risolte vulnerabilità in prodotti Cisco

nuova finestra - - CVE-2026-20342 : apre una nuova finestra - - CVE-2026-20341 : apre una nuova finestra - - CVE-2026-20340 : apre una nuova finestra - - CVE-2026-20336 : apre una nuova finestra - - CVE-2026-20335 : apre una nuova finestra - - CVE-2026-20334 : apre una nuova finestra - - CVE-2026-20333 : apre una nuova finestra - - CVE-2026-20332 : apre una nuova finestra - - CVE-2026-20331 : apre una nuova finestra - - CVE-2026-20330 : apre una nuova finestra - - CVE-2026-20329 : apre una nuova finestra - - CVE-2026-20326 : apre una nuova finestra - - CVE-2026-20325 : apre una nuova finestra - - CVE-2026-20324 : apre una nuova finestra - - CVE-2026-20323 : apre una nuova finestra - - CVE-2026-20322 : apre una nuova finestra - - CVE-2026-20307 : apre una nuova finestra - - CVE-2026-20306 : apre una nuova finestra - - CVE-2026-20305 : apre una nuova finestra - - CVE-2026-20300 : apre una nuova finestra - - CVE-2026-20295 : apre una nuova finestra - - CVE-2026-20284 : apre una nuova finestra - - CVE-2026-20250 : apre una nuova finestra - - CVE-2026-20249 : apre una nuova finestra - - CVE-2026-20247 : apre una nuova finestra - - CVE-2026-20242 : apre una nuova finestra - - CVE-2026-20237 : apre una nuova finestra - - CVE-2026-20234 : apre una nuova finestra - - CVE-2026-20222 : apre una nuova fi

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 availability varies by product
Affected
Fixed
No fixed version is explicitly recorded in the structured CVE data.
Action
Use the product-specific evidence above. Patch only products with a verified fixed release, and keep every affected or under-investigation state without a matching fix in the remediation queue.
Workaround
No verified workaround is recorded. Limit untrusted access and use least privilege until authoritative guidance is available.
04

Evidence and provenance

Published 16 Sept 2026 · Last source change 17 Sept 2026, 11:39 UTC · CWE-295 · Improper Certificate Validation

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 2026-09-17
European sourceENISA EUVD · EUVD-2026-81139
Product sourceVendor CSAF · Cisco PSIRT
Remediation sourceVendor CSAF · Cisco PSIRT
CWE sourceCNA
NVD statusNVD awaiting enrichment

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

Material change intelligence

What changed after publication

View recent updates ↗
  1. ENISA EUVD mappingEUVD-2026-81139 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-81139"}
    ENISA EUVD ↗
  2. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
  3. Remediation statusRemediation status changed from Awaiting fix to Mitigation available.
    Before
    Awaiting fix
    After
    Mitigation available
    Cisco PSIRT ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Remediation guidance recorded
ENISA EUVD · EUVD-2026-81139↗CVE authority or vendor reference · Cisco CISCO-SA-FMCFTD-SFTUN-MULTIVULNS-WGVHORN3↗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-2026-20323 · cve.blacktree.nl