CVE-2026-20355 (GCVE-0-2026-20355)
Vulnerability from cvelistv5 – Published: 2026-09-02 16:14 – Updated: 2026-09-02 17:58
VLAI
EPSS
VEX
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)
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
1 reference
Impacted products
1 product
| 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 |
guessed |
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Experimental. This forecast is provided for visualization only and may change without notice. Do not use it for operational decisions.
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
| Author | Source | Type | Date | Other |
|---|
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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The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the
vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base
model, served locally by ML-Gateway.
They have not been verified by an analyst and are provided for guidance only.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
The approach is described in our paper Mapping CVEs to MITRE ATT&CK Techniques: A Curated Gold-Set Classifier and the Limits of LLM-Assisted Label Expansion.
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