Medium Denial of service

CVE-2026-20054 — Cisco Secure Firewall Threat Defense Software Snort 3 Visual Basic for Application Infinite Loop Denial of Service Vulnerability

Multiple Cisco products are affected by a vulnerability in the Snort 3 VBA feature that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to crash.  This vulnerability is due to improper error checking when decompressing VBA data. An attacker could exploit this vulnerability by sending crafted VBA data to the Snort 3 Detection Engine on the targeted device. A successful exploit could allow the attacker to cause the Snort 3 Detection Engine to enter an infinite loop, causing a DoS condition.

Published Mar 4, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: cisco

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.4% (30-day exploitation probability)+6
Technical severity (medium)+3
Automatable exploitation (SSVC)+3

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.45%

ahead of 37% of scored CVEs · Oct 14, 2026

Affects

Cisco

Cisco Secure Firewall Threat Defense (FTD) Software and 5 more

CVSS base

5.8

Medium · 2 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

None

none · proof-of-concept · active

Automatable

Yes

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

Documented mitigation — sec.cloudapps.cisco.com (NIST National Vulnerability Database)

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Cisco Cisco Secure Firewall Threat Defense (FTD) Software, Cisco Cisco UTD SNORT IPS Engine Software, Cisco Cyber Vision…).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
Apply the documented mitigations until a definitive fix is available.
Search available logs for exploit probes matching the vulnerability class (denial of service), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Cisco	Cisco Secure Firewall Threat Defense (FTD) Software	version 7.2.0version 7.2.0.1version 7.2.1version 7.3.0version 7.2.2version 7.2.3version 7.3.1version 7.2.4 and 29 more version 7.2.5version 7.2.4.1version 7.3.1.1version 7.4.0version 7.2.5.1version 7.4.1version 7.2.6version 7.4.1.1version 7.2.7version 7.2.5.2version 7.3.1.2version 7.2.8version 7.6.0version 7.4.2version 7.2.8.1version 7.4.2.1version 7.2.9version 7.7.0version 7.4.2.2version 7.2.10version 7.6.1version 7.4.2.3version 7.6.2version 7.7.10version 7.6.2.1version 7.7.10.1version 7.4.2.4version 7.2.10.2version 7.4.3	Vulnerable	CVE Program (cve.org) e CISA ADP
Cisco	Cisco UTD SNORT IPS Engine Software	version 17.12.5cversion 17.12.4bversion 17.15.2aversion 17.12.5version 17.17.1version 17.12.5aversion 17.9.7aversion 17.15.3a and 95 more version 17.15.3version 17.12.5bversion 17.9.5fversion 17.15.4version 17.9.7bversion 17.18.1version 17.18.1aversion 17.12.6version 17.9.8version 17.15.4cversion 17.12.5dversion 17.18.2version 17.12.4version 17.3.8aversion 17.6.6aversion 17.9.4aversion 17.12.2version 17.13.1aversion 17.9.5aversion 17.12.3version 17.6.7version 17.14.1aversion 17.3.8version 17.12.3aversion 17.15.1aversion 17.6.8version 17.9.6version 17.6.8aversion 17.16.1aversion 17.9.5eversion 17.12.4aversion 17.15.2cversion 3.17.1Sversion 16.12.3version Fuji-16.9.5version 16.12.4version 17.3.1aversion 16.6.6version 16.12.2version Fuji-16.9.6version 3.17.0Sversion Fuji-16.9.3version Denali-16.3.7version Fuji-16.9.2version Fuji-16.9.4version Everest-16.6.4version Everest-16.6.3version 16.6.5version Denali-16.3.5version 17.2.1rversion 17.1.1version Everest-16.6.2version 16.6.7aversion Denali-16.3.4version 16.6.1version Denali-16.3.9version Denali-16.3.3version 16.12.1aversion 17.3.2version 17.4.1aversion 16.12.5version 17.5.1version Fuji-16.9.7version 16.6.9version 17.3.3version 17.5.1aversion 17.3.4version 17.3.4aversion 17.4.2version 17.4.1bversion 17.6.1aversion 16.6.10version 17.7.1aversion 16.12.6version Fuji-16.9.8version 17.6.2version 17.8.1aversion 16.12.7version 17.3.5version 17.6.3version 17.6.3aversion 17.7.2version 17.9.1aversion 17.6.4version 17.10.1aversion 17.3.6version 16.12.8version 17.3.7version 17.9.2aversion 17.6.5version 17.11.1aversion 17.9.3aversion 17.12.1aversion 17.9.4version 17.6.6	Vulnerable	CVE Program (cve.org) e CISA ADP
Cisco	Cyber Vision	version 3.0.0version 3.0.1version 3.0.2version 3.0.3version 3.0.4version 3.0.5version 3.0.6version 3.1.0 and 45 more version 3.1.1version 3.1.2version 3.2.0version 3.2.1version 3.2.2version 3.2.3version 3.2.4version 4.0.0version 4.0.1version 4.0.2version 4.0.3version 4.1.0version 4.1.1version 4.1.2version 4.1.3version 4.1.4version 4.1.5version 4.1.6version 4.1.7version 4.2.0version 4.2.1version 4.2.2version 4.2.3version 4.2.4version 4.2.6version 4.3.0version 4.3.1version 4.3.2version 4.3.3version 4.4.0version 4.4.1version 4.4.2version 4.4.3version 5.0.0version 5.0.1version 5.0.2version 5.1.0version 5.1.1version 5.1.2version 5.1.3version 5.2.0version 5.2.1version 5.3.0version 5.3.1version 5.3.2	Vulnerable	NIST National Vulnerability Database
Cisco	Cyber Vision	version 3.0.0version 3.0.2version 3.0.3version 3.0.1version 3.1.0version 3.0.4version 3.1.1version 3.1.2 and 46 more version 3.2.0version 3.0.5version 3.2.1version 3.0.6version 3.2.2version 3.2.3version 3.2.4version 4.0.0version 4.0.1version 4.0.2version 4.0.3version 4.1.0version 4.1.1version 4.1.2version 4.1.3version 4.1.4version 4.2.0version 4.2.1version 4.1.5version 4.2.2version 4.2.Xversion 4.2.3version 4.2.4version 4.2.6version 4.1.6version 4.3.0version 4.3.1version 4.3.2version 4.3.3version 4.4.0version 4.4.1version 4.4.2version 4.4.3version 4.1.7version 5.0.0version 5.0.1version 5.0.2version 5.1.0version 5.1.1version 5.1.2version 5.1.3version 5.2.0version 5.2.1version 5.3.0version 5.3.1version 5.3.2	Vulnerable	CVE Program (cve.org) e CISA ADP
Cisco	Secure Firewall Threat Defense	version 7.2.0version 7.2.0.1version 7.2.1version 7.2.2version 7.2.3version 7.2.4version 7.2.4.1version 7.2.5 and 29 more version 7.2.5.1version 7.2.5.2version 7.2.6version 7.2.7version 7.2.8version 7.2.8.1version 7.2.9version 7.2.10version 7.2.10.2version 7.3.0version 7.3.1version 7.3.1.1version 7.3.1.2version 7.4.0version 7.4.1version 7.4.1.1version 7.4.2version 7.4.2.1version 7.4.2.2version 7.4.2.3version 7.4.2.4version 7.4.3version 7.6.0version 7.6.1version 7.6.2version 7.6.2.1version 7.7.0version 7.7.10version 7.7.10.1	Vulnerable	NIST National Vulnerability Database
Cisco	Snort	≥ 3.0.0-233 and < 3.9.3.0	Vulnerable	NIST National Vulnerability Database
Cisco	Unified Threat Defense Snort Intrusion Prevention System Engine	version 17.9.5aversion 17.9.5eversion 17.9.5fversion 17.9.6version 17.9.7aversion 17.9.7bversion 17.9.8version 17.10.1a and 7 more version 17.11.1aversion 17.12.1aversion 17.12.2version 17.12.3version 17.12.3aversion 17.12.4version 17.12.4a	Vulnerable	NIST National Vulnerability Database

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Changed

Confidentiality

None

Integrity

None

Availability

Low

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
5.8	CVSS 3.1	Medium	3.9	1.4	psirt@cisco.com via NIST National Vulnerability Database
5.8	CVSS 3.1	Medium	—	—	cisco via CVE Program (cve.org) e CISA ADP

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L (score shown at the top: psirt@cisco.com)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-835 · Infinite Loop

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.45%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Track CPU/memory spikes and availability drops correlated with request patterns.

web/proxy/WAF logsnetwork IDS/IPSresource metrics

Timeline

What happened to this CVE, newest first.

2026
Affected products added · cisco/cisco cyber vision, cisco/cisco secure firewall threat defense (ftd) software, cisco/cisco utd snort ips engine so
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
Fix documented
Oct 13, 2026 · NIST National Vulnerability Database
CVSS changed · 5.8
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Mar 4, 2026 · cisco

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-ftd-snort3-vba
Vendor Advisory, Mitigation, NIST National Vulnerability Database

Elsewhere on this site

Cisco
every CVE for this vendor

Denial of service
same class

CWE-835
other pages naming this weakness

Related CVEs (same products)

High CVE-2026-20349 Cisco Secure Firewall Adaptive Security Appliance (ASA) and Secure Firewall Threat Defense (FTD) Heap Inspection Vulnerability KEV Aug 11, 2026
High CVE-2026-20012 Missing Release of Memory after Effective Lifetime in Cisco Secure Firewall Threat Defense Mar 25, 2026
Medium CVE-2026-20064 NULL Pointer Dereference in Cisco Secure Firewall Threat Defense Mar 4, 2026
Medium CVE-2026-20025 Integer Overflow or Wraparound in Cisco Secure Firewall Threat Defense Mar 4, 2026
Medium CVE-2026-20024 Buffer Errors (Improper Restriction of Operations within Memory Bounds) in Cisco Adaptive Security Appliance Software Mar 4, 2026
Medium CVE-2026-20023 Out-of-bounds Write in Cisco Secure Firewall Threat Defense Mar 4, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-20054 is "Cisco Secure Firewall Threat Defense Software Snort 3 Visual Basic for Application Infinite Loop Denial of Service Vulnerability", rated Medium. It affects Cisco Secure Firewall Threat Defense (FTD) Software (Cisco); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 5.8 describes technical severity. EPSS 0.45% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

Comments

Moderated technical discussion. Read the community guidelines.

No comments yet.