FKIE_CVE-2026-20355
Vulnerability from fkie_nvd - Published: 2026-09-02 17:17 - Updated: 2026-09-02 19:23
Severity
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.
References
Impacted products
| Vendor | Product | Version |
|---|
{
"affected": [
{
"affectedData": [
{
"defaultStatus": "unknown",
"product": "Cisco Secure Email",
"vendor": "Cisco",
"versions": [
{
"status": "affected",
"version": "14.0.0-698"
},
{
"status": "affected",
"version": "13.5.1-277"
},
{
"status": "affected",
"version": "13.0.0-392"
},
{
"status": "affected",
"version": "14.2.0-620"
},
{
"status": "affected",
"version": "13.0.5-007"
},
{
"status": "affected",
"version": "13.5.4-038"
},
{
"status": "affected",
"version": "14.2.1-020"
},
{
"status": "affected",
"version": "14.3.0-032"
},
{
"status": "affected",
"version": "15.0.0-104"
},
{
"status": "affected",
"version": "15.0.1-030"
},
{
"status": "affected",
"version": "15.5.0-048"
},
{
"status": "affected",
"version": "15.5.1-055"
},
{
"status": "affected",
"version": "15.5.2-018"
},
{
"status": "affected",
"version": "16.0.0-050"
},
{
"status": "affected",
"version": "15.0.3-002"
},
{
"status": "affected",
"version": "16.0.0-054"
},
{
"status": "affected",
"version": "15.5.3-022"
},
{
"status": "affected",
"version": "16.0.1-017"
},
{
"status": "affected",
"version": "15.5.4-012"
},
{
"status": "affected",
"version": "16.0.4-016"
},
{
"status": "affected",
"version": "15.0.5-016"
},
{
"status": "affected",
"version": "16.0.2-112"
},
{
"status": "affected",
"version": "16.0.3-044"
},
{
"status": "affected",
"version": "16.5.0-780"
}
]
}
],
"source": "psirt@cisco.com"
}
],
"cveTags": [],
"descriptions": [
{
"lang": "en",
"value": "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.\r\n\r\nThese 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."
}
],
"id": "CVE-2026-20355",
"lastModified": "2026-09-02T19:23:13.660",
"metrics": {
"cvssMetricV31": [
{
"cvssData": {
"attackComplexity": "HIGH",
"attackVector": "NETWORK",
"availabilityImpact": "NONE",
"baseScore": 5.9,
"baseSeverity": "MEDIUM",
"confidentialityImpact": "HIGH",
"integrityImpact": "NONE",
"privilegesRequired": "NONE",
"scope": "UNCHANGED",
"userInteraction": "NONE",
"vectorString": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N",
"version": "3.1"
},
"exploitabilityScore": 2.2,
"impactScore": 3.6,
"source": "psirt@cisco.com",
"type": "Secondary"
}
],
"ssvcV203": [
{
"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
"ssvcData": {
"id": "CVE-2026-20355",
"options": [
{
"exploitation": "none"
},
{
"automatable": "no"
},
{
"technicalImpact": "partial"
}
],
"role": "CISA Coordinator",
"timestamp": "2026-09-02T16:49:13.406894Z",
"version": "2.0.3"
}
}
]
},
"published": "2026-09-02T17:17:34.027",
"references": [
{
"source": "psirt@cisco.com",
"url": "https://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-smime-disc-dzw4rEdY"
}
],
"sourceIdentifier": "psirt@cisco.com",
"vulnStatus": "Awaiting Analysis",
"weaknesses": [
{
"description": [
{
"lang": "en",
"value": "CWE-345"
}
],
"source": "psirt@cisco.com",
"type": "Secondary"
}
]
}
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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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