CVE-2026-20011
Multiple Cisco Products Snort 3 SMTP MIME Denial of Service Vulnerability
CVE-2026-20011: Multiple Cisco Products Snort 3 SMTP MIME Denial of Service Vulnerability. Not in the CISA KEV catalog.
Compare the source-linked records below. Ratings and product/version details belong to each advisory; they are not a single CVE-wide score or proof that every listed product is affected. How VulniPulse collects and checks evidence.
CVE-2026-20011 at a glance
- CISA KEV
- Not listed (catalog checked )
- Highest advisory severity
- Medium
- CVSS base score
- 5.8 (Cisco)
- Fixed releases
- Cisco: 3.10.1.0, 17.12.8, 17.15.6, 17.18.5, 26.1.2, 26.2.1
- Vendor advisories
- 2 from Cisco
- VulniPulse record
- Published · Updated
Scores, vectors, weaknesses and fixed releases are quoted from vendor advisories that cover only CVE-2026-20011; bulletin-wide values are not repeated here.
Is CVE-2026-20011 exploited?
No exploitation is reported in the sources VulniPulse tracks: CVE-2026-20011 is not in the CISA KEV catalog (checked ) and no tracked advisory for it reports exploitation. That is not proof the vulnerability cannot be exploited.
How do I fix CVE-2026-20011?
Upgrade to a fixed release named by the vendor:
- Cisco: 3.10.1.0, 17.12.8, 17.15.6, 17.18.5, 26.1.2, 26.2.1
- Upgrade to the first fixed release for your train per the Fixed Releases table in this advisory. (Cisco)
- Release 3.x: upgrade to 3.10.1.0. (Cisco)
Vendor advisory comparison
Cisco
2 advisories- Advisory severityMedium5.8
Medium [CVE-2026-20011] Multiple Cisco Products Snort 3 SMTP MIME Denial of Service Vulnerability
cisco-sa-snort3-mime-vulns-bkXjcKktSource published Source updated
Multiple Cisco products are affected by a vulnerability in the Snort 3 SMTP MIME Decoder that could allow an unauthenticated, remote attacker to cause the Snort 3 Detection Engine to restart. This vulnerability is due to a lack of error checking when the MIME fields of the SMTP header are parsed. An attacker could exploit this vulnerability by sending crafted SMTP packets through an established connection to be parsed by Snort 3. A successful exploit could allow the attacker to cause a denial of service (DoS) condition when the Snort 3 Detection Engine unexpectedly restarts. Cisco has released software updates that address this vulnerability. There are no workarounds that address this vulnerability. This advisory is part of a group of advisories. For a complete list of the advisories and…
- Affected products in this advisory
- Secure Firewall Threat Defense (FTD) Software
- Firepower 2100 Series
- Firepower 1000 Series
- ASA 5500-X Series Firewalls
4 more entries in the full advisory.
- Source-reported affected versions
- Scope: For information about which products were affected by this vulnerability at the time of publication, see the following sections. Open Source Snort 3
- Release 3.x (first fixed: 3.10.1.0)
- Release 17.12 (first fixed: 17.12.8)
- Release 17.15 (first fixed: 17.15.6)
3 more entries in the full advisory.
- Source-reported fixed versions
- 3.10.1.0
- 17.12.8
- 17.15.6
- 17.18.5
2 more entries in the full advisory.
- Mitigation guidance
- Upgrade to the first fixed release for your train per the Fixed Releases table in this advisory.
- Release 3.x: upgrade to 3.10.1.0.
- Release 17.12: upgrade to 17.12.8.
- Release 17.15: upgrade to 17.15.6.
3 more entries in the full advisory.
- Workarounds
- There are no workarounds that address this vulnerability.
- Advisory severityUnrated
Advisory [CVE-2026-20011 +12] Cisco Advance Notification for Publication of October 21, 2026, Security Advisories
cisco-sa-notice-QGwHnJ6kSource published Source updated
This bulletin covers 13 CVEs. The products, versions, score and guidance below describe the bulletin; check its source for applicability to this specific CVE.
On October 21, 2026, the Cisco Product Security Incident Response Team (PSIRT) published the following advisories. To remediate the vulnerabilities that were disclosed on October 21, 2026, Cisco strongly recommends that customers upgrade to the fixed software that is indicated in the advisories. For more information about changes in Cisco PSIRT vulnerability disclosure, see Strengthening the Foundation: A Predictable, Customer-Focused Response to AI-Accelerated Vulnerability Discovery. Snort 3 Cisco Security Advisory CVE ID Security Impact Rating CVSS Base Score Critical 9.0 High 7.8 Medium 5.8 5.3 Cisco Expressway and Unified Communications Products
- Affected products in this advisory
- No product details extracted. Check the source bulletin.
- Source-reported affected versions
- Affected-version details not available in this record.
- Source-reported fixed versions
- No fixed-version detail extracted. This does not mean no fix exists.
- Mitigation guidance
- To remediate the vulnerabilities that were disclosed on October 21, 2026, Cisco strongly recommends that customers upgrade to the fixed software that is indicated in the advisories.
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