CVE-2026-20354

mediumpriority · track · 24EPSS 0.002 · 10 %ileNLUS
grimoire priorityP3 · Track
Exploitable?
—
no known exploitation
Likely / severe?
0.20% (10th) EPSS
CVSS 5.9 · medium
Is it mine?
32 products
Check your exposure
Who says so?
2 sources
cisco_csaf · ncsc_nl

EPSS · scored 2026-10-27

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.

01

remediations

Vendor fix, mitigation, or workaround guidance, as published by each source.

A vendor fix is available.

02

cvss

Technical severity, 0–10. One row per scoring source.

5.9
010

base score 0–10 · higher = more severe · hover a vector to decode

v3.15.9mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:Nprimary · psirt@cisco.com USexploitability 2.2 · impact 3.6
v3.15.4mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N/E:Usecondary · CVSS-BT (t0sche)
v3.15.9mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:Nsecondary · NCSC-NL NL
v3.15.9mediumCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:Nsecondary · Cisco PSIRT US
03

weaknesses

The CWE weakness classes this flaw belongs to.

CWE-354USCWE-354US
04

affected products (32)

Products and version ranges known to be affected.

showing 20 of 32
05

advisories (2)

Vendor and ecosystem advisories describing this.

  • NCSC-2026-0338Kwetsbaarheden verholpen in Cisco Nexus 9000 Series, IOS XR Software en Secure EmailNL2026-09-03csaf · ncsc_nlNL

    Cisco heeft kwetsbaarheden verholpen in Cisco Nexus 9000 Series Switches met Silicon One technologie, Cisco IOS XR Software en Cisco Secure Email.

  • cisco-sa-esa-smime-disc-dzw4rEdYCisco Secure Email Secure/Multipurpose Internet Mail Extensions Ciphertext Decryption Vulnerabilities2026-09-02csaf · cisco_csafUS

    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. There are no workarounds that address these vulnerabilities.

06

sources

Which sources assert this record, and when.

cisco_csafncsc_nlNVDCVE.orgMITRE
published 2026-09-02modified 2026-09-02
07

references (1) nvd

External citations — patches, advisories, analysis.

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