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CVE-2026-20355 (GCVE-0-2026-20355)

Vulnerability from cvelistv5 – Published: 2026-09-02 16:14 – Updated: 2026-09-02 17:58
VLAI
Title
Cisco Secure Email S/MIME Ciphertext Decryption Vulnerabilty
Summary
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.
Severity
5.9 (Medium)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-09-02 16:49 UTC
CWE
  • CWE-345 - Insufficient Verification of Data Authenticity
Assigner
References
Impacted products
Vendor Product Version CPE status
Cisco Cisco Secure Email Affected: 14.0.0-698
Affected: 13.5.1-277
Affected: 13.0.0-392
Affected: 14.2.0-620
Affected: 13.0.5-007
Affected: 13.5.4-038
Affected: 14.2.1-020
Affected: 14.3.0-032
Affected: 15.0.0-104
Affected: 15.0.1-030
Affected: 15.5.0-048
Affected: 15.5.1-055
Affected: 15.5.2-018
Affected: 16.0.0-050
Affected: 15.0.3-002
Affected: 16.0.0-054
Affected: 15.5.3-022
Affected: 16.0.1-017
Affected: 15.5.4-012
Affected: 16.0.4-016
Affected: 15.0.5-016
Affected: 16.0.2-112
Affected: 16.0.3-044
Affected: 16.5.0-780
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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


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