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Vulnerabilities

Vulnerability · CVE-2026-20011

Multiple Cisco Products Snort 3 SMTP MIME Denial of Service Vulnerability

Published Oct 21, 2026 · catalog updated Oct 22, 2026 · Cisco

Last checked Nov 6, 2026. A connected source was read within the last 7 days.

Check if you run it

No confirmed exploitation is on record for CVE-2026-20011. EPSS is 0.53%. Act only if a listed version of Cisco is installed.

Gaps on this record

  • No version range is stored. A customer cannot check an installed version against this record.
  • No vendor fix or required action is stored. Compare the linked advisory before you change production.
Severity
Medium5.8
Known exploitation
Not in CISA/VulnCheck KEV
EPSS
0.53%
Remediation
Advisory link
Affected products
Cisco

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. C

No affected version ranges are stored yet. Use the vendor advisory before you decide this record does not apply.

How to fix CVE-2026-20011

What to do

Three questions, each answered from this record only. Confirm the vendor advisory before you patch.

Should you patch?

No confirmed exploitation is on record for CVE-2026-20011. EPSS is 0.53%. Act only if a listed version of Cisco is installed.

Which versions are affected?

Affected version ranges are not on this record. Compare the installed version with the linked vendor advisory before you change production.

What should an analyst verify?

CWE-805. EPSS 0.53%. There is no CISA KEV listing. No Exploit-DB or Metasploit reference is linked. Use the source links for the original advisory.

Technology hubs

Cisco security

Code

The project this record applies to. Exploit listings stay in References.

No public source repository is identified for this product.

Timeline

Detection, updates, and resolution for this record.

  1. Oct 21, 2026 · NIST NVD

    Detected

    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 co

  2. Oct 22, 2026 · NIST NVD

    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 co

Sources

  • Cisco Security AdvisoriesVendor advisoryCVE-2026-20011

    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 h

    sec.cloudapps.cisco.com
  • CVE.orgVulnerability recordCVE-2026-20011

    Official CVE identifier

    cve.org
  • FIRST EPSSExploitation probabilityCVE-2026-20011

    30-day exploitation probability 0.53%

    first.org
  • NIST NVDVulnerability recordCVE-2026-20011

    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 SMT

    nvd.nist.gov

References

Freshness

Last verified in this catalog Nov 6, 2026. Significant claims (KEV, EPSS, CVSS, affected ranges) come from the source rows above — open the original publisher for the authoritative advisory.

  • FIRST EPSSNov 6, 2026
  • Cisco Security AdvisoriesNov 6, 2026
  • NIST NVDOct 22, 2026
  • CVE.orgOct 21, 2026