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CVE-2026-20066

MEDIUMCVSS 5.8/10EPSS 0.47%

Last modified

CVE-2026-20066 is a medium-severity vulnerability rated 5.8/10 on the CVSS scale. Multiple Cisco products are affected by a vulnerability in the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart, resulting in an interruption of packet inspection. This vulnerability is due to an error in the JSTokenizer normalization logic when the HTTP inspection normalizes JavaScript. An attacker could exploit this vulnerability by sending crafted HTTP packets through an established connection that is parsed by Snort 3. EPSS estimates a 0.47% chance of exploitation in the next 30 days.

Description

Multiple Cisco products are affected by a vulnerability in the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart, resulting in an interruption of packet inspection. This vulnerability is due to an error in the JSTokenizer normalization logic when the HTTP inspection normalizes JavaScript. An attacker could exploit this vulnerability by sending crafted HTTP packets through an established connection that is parsed by Snort 3. A successful exploit could allow the attacker to cause a DoS condition when the Snort 3 Detection Engine restarts unexpectedly. JSTokenizer is not enabled by default.

Metrics

CVSS 3.1
5.8/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:N/A:L

EPSS Probability
0.47%

37.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
CiscoCisco Secure Firewall Threat Defense (FTD) Software7.4.0; 7.4.1; 7.4.1.1; 7.6.0; 7.4.2; 7.4.2.1; 7.7.0; 7.4.2.2; 7.6.1; 7.4.2.3; 7.6.2; 7.7.10; 7.6.2.1; 7.7.10.1; 7.4.2.4; 7.4.3
CiscoCisco UTD SNORT IPS Engine Software17.3.1a; 17.2.1r; 17.3.2; 17.4.1a; 17.5.1; 17.3.3; 17.5.1a; 17.3.4; 17.3.4a; 17.4.2; 17.4.1b; 17.6.1a; 17.7.1a; 17.6.2; 17.8.1a; 17.3.5; 17.6.3; 17.6.3a; 17.7.2; 17.9.1a; 17.6.4; 17.10.1a; 17.3.6; 17.3.7; 17.9.2a; 17.6.5; 17.11.1a; 17.9.3a; 17.12.1a; 17.9.4; 17.6.6; 17.3.8; 17.3.8a; 17.6.6a; 17.9.4a; 17.12.2; 17.13.1a; 17.9.5a; 17.12.3; 17.6.7; 17.14.1a; 17.12.4; 17.12.3a; 17.15.1a; 17.6.8; 17.9.6; 17.6.8a; 17.16.1a; 17.9.5e; 17.12.4a; 17.15.2c; 17.9.5f; 17.12.4b; 17.15.2a; 17.12.5; 17.17.1; 17.12.5a; 17.9.7a; 17.15.3a; 17.15.3; 17.12.5b; 17.12.5c; 17.15.4; 17.9.7b; 17.18.1; 17.18.1a; 17.12.6; 17.9.8; 17.15.4c; 17.12.5d; 17.18.2

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-20066?
Multiple Cisco products are affected by a vulnerability in the Snort 3 Detection Engine that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart, resulting in an interruption of packet inspection. This vulnerability is due to an error in the JSTokenizer normalization logic when the HTTP inspection normalizes JavaScript. An attacker could exploit this vulnerability by sending crafted HTTP packets through an established connection that is parsed by Snort 3. A successful exploit could allow the attacker to cause a DoS condition when the Snort 3 Detection Engine restarts unexpectedly. JSTokenizer is not enabled by default.
How severe is CVE-2026-20066?
CVE-2026-20066 has a CVSS score of 5.8/10 (MEDIUM severity). The EPSS model estimates a 0.47% probability of exploitation in the next 30 days.
How do I fix CVE-2026-20066?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST