CVE Tools
Track your stack

CVE-2026-20355

Cisco Secure Email S/MIME Ciphertext Decryption Vulnerabilty

No known exploitation. EPSS puts it in the 10th percentile. No fix published yet.

CVSS 3.15.9MediumEPSS percentile10th0.2% chance in 30 daysCISA KEVNot listedNo confirmed exploitation
No public exploit knownFixNone yetNo fix or workaround published

Published Updated Sources: CVE.org, NVD

NVD CVE.org

What to do

No fixed build or workaround is published yet. Limit exposure and watch for a patch.

  • Cisco Secure EmailAffected: 14.0.0-698Upgrade to: not statedAffected: 13.5.1-277Upgrade to: not statedAffected: 13.0.0-392Upgrade to: not statedAffected: 14.2.0-620Upgrade to: not stated + 20 more branchesStated by: CVE record

Versions as the sources state them. Full version matrix after sign-in

Check it yourselfA free OpenVAS check exists for this CVE. Run it against your hosts.Is your organisation exposed?Request an assessment to establish which checks fit your systems.

What it is

From the CVE record

Multiple vulnerabilities in the Secure/Multipurpose Internet Mail Extensions (S/MIME) decryption functionality of Cisco Secure Email could allow an unauthenticated, remote attacker to recover plain text from encrypted email messages. These vulnerabilities are due to insufficient validation of message integrity. An attacker could exploit these vulnerabilities by using a machine-in-the-middle technique to intercept and modify traffic between email gateways. A successful exploit could allow the attacker to obtain plaintext content from the encrypted communication.

In plain language

No plain-language summary for this CVE yet.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS10th
CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

0.2% chance of exploitation activity in the next 30 days, which ranks it in the 10th percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

8 events over 3 days, from the signal feeds we watch.

  1. OpenVAS check added
  2. Publishedpublished, weakness classified, weakness classified, att&ck mapped, att&ck mapped, record updated

Affected products

Technical detail

CVSS 3.1 vector

Open in the CVSS calculator

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

Scored 5.9 by NVD.

How it is reached

  • Attack Vector NetworkExploitable remotely over the network without any special conditions
  • Attack Complexity HighRequires specific conditions like a race condition or non-default configuration
  • Privileges Required NoneNo authentication required — anyone can exploit this
  • User Interaction NoneNo user interaction needed — fully automated exploitation

Scope

  • Scope UnchangedImpact is limited to the vulnerable component itself

Impact if exploited

  • Confidentiality HighTotal information disclosure — all data in the component is compromised
  • Integrity NoneNo integrity impact
  • Availability NoneNo availability impact

Weaknesses

ATT&CK techniques

Mapped from the weaknesses above (CWE to ATT&CK), not observed in attacks.

Sources

References in the record

In the news

Watch the software you run.

My Stack ranks new CVEs for your products by real-world exploitation, so the next serious one reaches you without reading every advisory.

We'll flag the next CVE, public exploit or patch for Cisco Secure Email, not every advisory.