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Full vulnerability report · 2026
CVE-2026-20154High confidence

Cisco Secure Firewall Adaptive Security Appliance Software and Secure Firewall Threat Defense Software Logging Denial of Service

Cisco · Cisco Secure Firewall Adaptive Security Appliance (ASA) Software

Official source article: Cisco CISCO-SA-ASA-FTD-LOGGING-DOS-ZXXNESFN ↗. Check the applicable product and release in the original source.

8.6HighCVSS 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 1,171 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.
  • The selected CVSS metric records a network-reachable, unauthenticated path with no user interaction.
  • EPSS is 0.40% 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 Cisco Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 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 1,171 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-asa-ftd-logging-dos-ZXXNesfN · CSAF 2.0 · revision 1.1.0 · finalCisco PSIRTCisco Secure Firewall Adaptive Security Appliance Software and Secure Firewall Threat Defense Software Logging Denial of Service
1,171 known affected

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

  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.1 when installed on Cisco Firepower 2100 Series
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.1 when installed on Cisco Firepower 1000 Series
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.1 when installed on Cisco ASA 5500-X Series Firewalls
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.1 when installed on Cisco 3000 Series Industrial Security Appliances (ISA)
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.1 when installed on Cisco Firepower 9000 Series
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.1 when installed on Cisco Firepower 4100 Series
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.1 when installed on Cisco Adaptive Security Virtual Appliance (ASAv)
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.1.28 when installed on Cisco Firepower 2100 Series
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.1.28 when installed on Cisco Firepower 1000 Series
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.1.28 when installed on Cisco ASA 5500-X Series Firewalls
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.1.28 when installed on Cisco 3000 Series Industrial Security Appliances (ISA)
  • Cisco Secure Firewall Adaptive Security Appliance (ASA) Software 9.16.1.28 when installed on Cisco Firepower 9000 Series
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-2026-81128

No EUVD known-exploited evidence

A vulnerability in the system rate-limiting process for syslog message 419002 of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause high CPU utilization on an affected device, resulting in a denial of service (DoS) condition. This vulnerability is due to improper rate limiting for syslog message 419002. An attacker could exploit this vulnerability by sending a flood of TCP synchronization (SYN) packets to an affected device. A successful exploit could allow the attacker to cause high CPU utilization, resulting in performance degradation. 

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
8.6 · 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 1,171 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 system rate-limiting process for syslog message 419002 of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause high CPU utilization on an affected device, resulting in a denial of service (DoS) condition. This vulnerability is due to improper rate limiting for syslog message 419002. An attacker could exploit this vulnerability by sending a flood of TCP synchronization (SYN) packets to an affected device. A successful exploit could allow the attacker to cause high CPU utilization, resulting in performance degradation. 

What

A vulnerability in the system rate-limiting process for syslog message 419002 of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause high CPU utilization on an affected device, resulting in a denial of service (DoS) condition. This vulnerability is due to improper rate limiting for syslog message 419002. An attacker could exploit this vulnerability by sending a flood of TCP synchronization (SYN) packets to an affected device. A successful exploit could allow the attacker to cause high CPU utilization, resulting in performance degradation. 

Why

A malformed condition prevents a loop from making progress or terminating, allowing resource exhaustion.

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 system rate-limiting process for syslog message 419002 of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause high CPU utilization on an affected device, resulting in a denial of service (DoS) condition. This vulnerability is due to improper rate limiting for syslog message 419002. An attacker could exploit this vulnerability by sending a flood of TCP synchronization (SYN) packets to an affected device. A successful exploit could allow the attacker to cause high CPU utilization, resulting in performance degradation. 

Why

A malformed condition prevents a loop from making progress or terminating, allowing resource exhaustion.

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 → Loop with Unreachable Exit Condition ('Infinite Loop') → 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-835 ↗

CWE-835: Loop with Unreachable Exit Condition ('Infinite Loop'). The product contains an iteration or loop with an exit condition that cannot be reached, i.e., an infinite loop.

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-835
A

Official authority intelligence

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

ENISA EUVD · EUVD-2026-81128Official EUVD mapping

A vulnerability in the system rate-limiting process for syslog message 419002 of Cisco Secure Firewall Adaptive Security Appliance (ASA) Software and Cisco Secure Firewall Threat Defense (FTD) Software could allow an unauthenticated, remote attacker to cause high CPU utilization on an affected device, resulting in a denial of service (DoS) condition. This vulnerability is due to improper rate limiting for syslog message 419002. An attacker could exploit this vulnerability by sending a flood of TCP synchronization (SYN) packets to an affected device. A successful exploit could allow the attacker to cause high CPU utilization, resulting in performance degradation. 

Official EUVD record ↗
BSI · German · WID-SEC-2026-3422Cisco Secure FTD und ASA: Mehrere Schwachstellen

Ein Angreifer kann mehrere Schwachstellen in Cisco Secure Firewall Threat Defense und Cisco ASA (Adaptive Security Appliance) ausnutzen, um erweiterte Berechtigungen zu erlangen, Sicherheitsmaßnahmen zu umgehen, Daten zu manipulieren, sensible Informationen 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

US-dos-wR3hYPMw Bulletin de sécurité Cisco cisco-sa-ise-rce-se7bYU57 du 16 septembre 2026 https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ise-rce-se7bYU57 Bulletin de sécurité Cisco cisco-sa-ise-sql-inj-3QTKR947 du 16 septembre 2026 https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ise-sql-inj-3QTKR947 Support ISE Cisco https://www.cisco.com/c/en/us/support/security/identity-services-engine/series.html Référence CVE CVE-2026-20130 https://www.cve.org/CVERecord?id=CVE-2026-20130 Référence CVE CVE-2026-20135 https://www.cve.org/CVERecord?id=CVE-2026-20135 Référence CVE CVE-2026-20154 https://www.cve.org/CVERecord?id=CVE-2026-20154 Référence CVE CVE-2026-20176 https://www.cve.org/CVERecord?id=CVE-2026-20176 Référence CVE CVE-2026-20192 https://www.cve.org/CVERecord?id=CVE-2026-20192 Référence CVE CVE-2026-20194 https://www.cve.org/CVERecord?id=CVE-2026-20194 Référence CVE CVE-2026-20211 https://www.cve.org/CVERecord?id=CVE-2026-20211 Référence CVE CVE-2026-20222 https://www.cve.org/CVERecord?id=CVE-2026-20222 Référence CVE CVE-2026-20234 https://www.cve.org/CVERecord?id=CVE-2026-20234 Référence CVE CVE-2026-20237 https://www.cve.org/CVERecord?id=CVE-2026-20237 Référence CVE CVE-2026-20242 https://www.cve.org/CVERecord?id=

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

nuova finestra - - CVE-2026-20300 : 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 finestra - - CVE-2026-20211 : apre una nuova finestra - - CVE-2026-20194 : apre una nuova finestra - - CVE-2026-20192 : apre una nuova finestra - - CVE-2026-20176 : apre una nuova finestra - - CVE-2026-20154 : apre una nuova finestra - - CVE-2026-20135 : apre una nuova finestra - - CVE-2026-20130 : apre una nuova finestra - - Riferimenti (20) https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ISE-ABP-VNSW7Tn5 https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-fmc2-multivulns-HXgcqRG https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ise-multi-hrP9jQSQ https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-hardening-ndw1-psFvnrg https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cis

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. If business-safe, reduce exposure to the affected interface and allow only trusted sources until authoritative guidance is available.
04

Evidence and provenance

Published 16 Sept 2026 · Last source change 18 Sept 2026, 19:09 UTC · CWE-835 · Loop with Unreachable Exit Condition ('Infinite Loop')

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-2026-81128
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. Remediation statusRemediation status changed from Awaiting fix to Mitigation available.
    Before
    Awaiting fix
    After
    Mitigation available
    Cisco PSIRT ↗
  2. ENISA EUVD mappingEUVD-2026-81128 was added to the official ENISA EUVD mapping for this CVE.
    Before
    not recorded
    After
    {"euvdId":"EUVD-2026-81128"}
    ENISA EUVD ↗
  3. Catalogue recordCVE added to the BlackTree catalogue.
    CNA ↗
Material fields only · duplicate refreshes suppressed · history retained for the configured operational retention period
CVE published
Remediation guidance recorded
ENISA EUVD · EUVD-2026-81128↗CVE authority or vendor reference · Cisco CISCO-SA-ASA-FTD-LOGGING-DOS-ZXXNESFN↗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-2026-20154 · cve.blacktree.nl