FKIE_CVE-2026-20355

Vulnerability from fkie_nvd - Published: 2026-09-02 17:17 - Updated: 2026-09-02 19:23
Severity
5.9 (Medium) - CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
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
psirt@cisco.comhttps://sec.cloudapps.cisco.com/security/center/content/CiscoSecurityAdvisory/cisco-sa-esa-smime-disc-dzw4rEdY
Impacted products
Vendor Product Version
To clipboard 

{
  "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"
    }
  ]
}



Log in or create an account to share your comment.




Tags
Taxonomy of the tags.




Drag nodes to arrange them. Double-click a related vulnerability to open it, or a source to visit its link. The Physics button on the left tunes the layout and the simulation; the legend at the bottom left hides or shows nodes by kind and by sighting type.

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.
Vulnerability timeline

Sightings and recorded dates, grouped by day · UTC

JSON

Loading timeline…




    Related by attack behaviour

    Vulnerabilities whose description is nearest to this one in the vector space of the CIRCL/vulnerability-attack-technique-biencoder model. This is a similarity search over the bi-encoder space (plain cosine), not a classification, and it has no measured accuracy.