Cyber Resilience

CVE-2026-20054

DoS in Cisco Unified Threat Defense Snort Intrusion Prevention System Engine 16.12.1a … fuji-16.9.8

DoS
Published
04 March 2026
Modified
20 August 2026
Patch / advisory
View advisory
CVSS Score v3.1 5.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L
EPSS Score 0.0043 36th percentile
Risk Priority 46 floored blend · peak EPSS

CVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.

Summary

CVE-2026-20054 is a medium-severity Infinite Loop (CWE-835) vulnerability in Cisco Unified Threat Defense Snort Intrusion Prevention System Engine. Its CVSS base score is 5.8 (Medium).

Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 36th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog.

The strongest mitigations our analysis identified map to SA-11 (Developer Testing and Evaluation) and SI-2 (Flaw Remediation) — see the control section below for these in your framework.

EU & UK References

Vulnerability Data

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…

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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.

CWE(s)
CWE-835

Related Threats

MITRE ATT&CK Enterprise Techniques

T1499.004 Application or System Exploitation Impact
Adversaries may exploit software vulnerabilities that can cause an application or system to crash and deny availability to users.
attack.mitre.org →
T1499 Endpoint Denial of Service Impact
Adversaries may perform Endpoint Denial of Service (DoS) attacks to degrade or block the availability of services to users.
attack.mitre.org →
T1499.003 Application Exhaustion Flood Impact
Adversaries may target resource intensive features of applications to cause a denial of service (DoS), denying availability to those applications.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2026-20068Same product: Cisco Cyber Vision
CVE-2023-20083Same product: Cisco Secure Firewall Threat Defense
CVE-2024-20353Same product: Cisco Secure Firewall Threat Defense
CVE-2026-20057Same product: Cisco Cyber Vision
CVE-2023-25653Same vendor: Cisco
CVE-2026-20053Same product: Cisco Cyber Vision
CVE-2026-20067Same product: Cisco Cyber Vision
CVE-2023-20116Same vendor: Cisco
CVE-2026-20065Same product: Cisco Secure Firewall Threat Defense
CVE-2026-20066Same product: Cisco Secure Firewall Threat Defense

Affected Assets

cisco
snort
3.0.0-233 — 3.9.3.0
cisco
cyber vision
3.0.0, 3.0.1, 3.0.2, 3.0.3, 3.0.4
cisco
secure firewall threat defense
7.2.0, 7.2.0.1, 7.2.1, 7.2.10, 7.2.10.2
cisco
unified threat defense snort intrusion prevention system engine
16.12.1a, 16.12.2, 16.12.3, 16.12.4, 16.12.5

Mitigating Controls

Mitigating Controls (NIST 800-53 r5) AI

SA-11 Developer Testing and Evaluation good match

Developer testing and evaluation can discover unreachable loop exit conditions through static analysis, fuzzing, or execution tracing.

SI-2 Flaw Remediation good match

Flaw remediation processes identify and correct infinite-loop defects reported from testing or operations.

SA-15 Development Process, Standards, and Tools partial match

Requiring documented development processes and secure coding standards reduces introduction of loops whose termination conditions are unreachable.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure SDLC practices (reviews, testing, static analysis) directly prevent introduction of infinite-loop defects.

ID.RA-01 partial match
prevents

Static analysis and vuln scanning during asset assessment can detect unreachable loop exits.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing can uncover infinite-loop conditions before release.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates practices that can detect and prevent infinite-loop defects.

A.8.26 Application security requirements partial match
prevents

Application security requirements can specify loop-termination rules, indirectly reducing the weakness.

A.8.28 Secure coding partial match
prevents

Secure coding standards directly address loop termination and prevent infinite loops.

References