Packet-inspection interruption via JSTokenizer normalization error
Published Mar 4, 2026 · Updated Mar 4, 2026
Denial of service in Cisco FTD and UTD Snort IPS software allows remote attackers to restart packet inspection with crafted HTTP packets. The JSTokenizer logic enters an error condition while normalizing JavaScript from HTTP traffic inspected by the Snort 3 Detection Engine. Exploitation requires an established connection parsed by Snort 3 and the nondefault JSTokenizer feature; the restart interrupts packet inspection.
Summary
What happened
Denial of service in Cisco FTD and UTD Snort IPS software allows remote attackers to restart packet inspection with crafted HTTP packets. The JSTokenizer logic enters an error condition while normalizing JavaScript from HTTP traffic inspected by the Snort 3 Detection Engine. Exploitation requires an established connection parsed by Snort 3 and the nondefault JSTokenizer feature; the restart interrupts packet inspection.
The record
- CVE
- CVE-2026-20066
- Published
- Mar 4, 2026
- Updated
- Mar 4, 2026
- Vendor
- ClamAV
- Product
- Cisco UTD Snort IPS Engine Software
- Classifications
- CWE-400, T1499
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 4, 2026CVE publishedPublication date reported by the CVE source.
- Mar 4, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=17.10.1a
- Affected versionversion=17.11.1a
- Affected versionversion=17.12.1a
- Affected versionversion=17.12.2
- Affected versionversion=17.12.3
- Affected versionversion=17.12.3a
- Affected versionversion=17.12.4
- Affected versionversion=17.12.4a
- Affected versionversion=17.12.4b
- Affected versionversion=17.12.5
- Affected versionversion=17.12.5a
- Affected versionversion=17.12.5b
- Affected versionversion=17.12.5c
- Affected versionversion=17.12.5d
- Affected versionversion=17.12.6
- Affected versionversion=17.13.1a
- Affected versionversion=17.14.1a
- Affected versionversion=17.15.1a
- Affected versionversion=17.15.2a
- Affected versionversion=17.15.2c
- Affected versionversion=17.15.3
- Affected versionversion=17.15.3a
- Affected versionversion=17.15.4
- Affected versionversion=17.15.4c
- Affected versionversion=17.16.1a
- Affected versionversion=17.17.1
- Affected versionversion=17.18.1
- Affected versionversion=17.18.1a
- Affected versionversion=17.18.2
- Affected versionversion=17.2.1r
- Affected versionversion=17.3.1a
- Affected versionversion=17.3.2
- Affected versionversion=17.3.3
- Affected versionversion=17.3.4
- Affected versionversion=17.3.4a
- Affected versionversion=17.3.5
- Affected versionversion=17.3.6
- Affected versionversion=17.3.7
- Affected versionversion=17.3.8
- Affected versionversion=17.3.8a
- Affected versionversion=17.4.1a
- Affected versionversion=17.4.1b
- Affected versionversion=17.4.2
- Affected versionversion=17.5.1
- Affected versionversion=17.5.1a
- Affected versionversion=17.6.1a
- Affected versionversion=17.6.2
- Affected versionversion=17.6.3
- Affected versionversion=17.6.3a
- Affected versionversion=17.6.4
- Affected versionversion=17.6.5
- Affected versionversion=17.6.6
- Affected versionversion=17.6.6a
- Affected versionversion=17.6.7
- Affected versionversion=17.6.8
- Affected versionversion=17.6.8a
- Affected versionversion=17.7.1a
- Affected versionversion=17.7.2
- Affected versionversion=17.8.1a
- Affected versionversion=17.9.1a
- Affected versionversion=17.9.2a
- Affected versionversion=17.9.3a
- Affected versionversion=17.9.4
- Affected versionversion=17.9.4a
- Affected versionversion=17.9.5a
- Affected versionversion=17.9.5e
- Affected versionversion=17.9.5f
- Affected versionversion=17.9.6
- Affected versionversion=17.9.7a
- Affected versionversion=17.9.7b
- Affected versionversion=17.9.8
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
No public exploit references are available in this record.
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
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Your stack
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