Vulnerability-Lookup

OESA-2026-4104 (CVE-2026-63435)

Vulnerability from osv_openeuler – Published: 2026-09-25 01:28 – Updated: 2026-09-25 01:28 – Source website

Summary

rubygem-mail security update

Details

A really Ruby Mail handler.

Security Fix(es):

Affected versions of this package are vulnerable to Improper Validation of Syntactic Correctness of Input through q_value_decode and b_value_decode in lib/mail/utilities.rb. An attacker can make a display name or local part decode to a different address than intended by supplying a malformed RFC 2047 encoded-word, including one that embeds extra encoded-word markers or additional text. The decoders only matched the first encoded-word and used a greedy charset capture, so a crafted header could cause the parsed From, To, or Reply-To value to omit or reshuffle literal text. Applications that display, compare, or authorize based on the decoded address can then present or act on a spoofed sender or recipient address.(CVE-2026-63435)

Severity

5.3 (Medium)


                    
                      CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

References

URL

Type

	https://www.openeuler.org/zh/security/security-bu…	ADVISORY
	https://nvd.nist.gov/vuln/detail/CVE-2026-63435	ADVISORY

JSON

To clipboard

{
  "affected": [
    {
      "ecosystem_specific": {
        "noarch": [
          "rubygem-mail-2.8.1-2.oe2403sp1.noarch.rpm",
          "rubygem-mail-doc-2.8.1-2.oe2403sp1.noarch.rpm"
        ],
        "src": [
          "rubygem-mail-2.8.1-2.oe2403sp1.src.rpm"
        ]
      },
      "package": {
        "ecosystem": "openEuler:24.03-LTS-SP1",
        "name": "rubygem-mail",
        "purl": "pkg:rpm/openEuler/rubygem-mail\u0026distro=openEuler-24.03-LTS-SP1"
      },
      "ranges": [
        {
          "events": [
            {
              "introduced": "0"
            },
            {
              "fixed": "2.8.1-2.oe2403sp1"
            }
          ],
          "type": "ECOSYSTEM"
        }
      ]
    }
  ],
  "database_specific": {
    "severity": "Medium"
  },
  "details": "A really Ruby Mail handler.\r\n\r\nSecurity Fix(es):\n\nAffected versions of this package are vulnerable to Improper Validation of Syntactic Correctness of Input through `q_value_decode` and `b_value_decode` in `lib/mail/utilities.rb`. An attacker can make a display name or local part decode to a different address than intended by supplying a malformed RFC 2047 encoded-word, including one that embeds extra encoded-word markers or additional text. The decoders only matched the first encoded-word and used a greedy charset capture, so a crafted header could cause the parsed `From`, `To`, or `Reply-To` value to omit or reshuffle literal text. Applications that display, compare, or authorize based on the decoded address can then present or act on a spoofed sender or recipient address.(CVE-2026-63435)",
  "id": "OESA-2026-4104",
  "modified": "2026-09-25T01:28:27Z",
  "published": "2026-09-25T01:28:27Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://www.openeuler.org/zh/security/security-bulletins/detail/?id=openEuler-SA-2026-4104"
    },
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-63435"
    }
  ],
  "schema_version": "1.7.2",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
      "type": "CVSS_V3"
    }
  ],
  "summary": "rubygem-mail security update",
  "upstream": [
    "CVE-2026-63435"
  ]
}

CVE-2026-63435 (GCVE-0-2026-63435)

Vulnerability from cvelistv5 – Published: 2026-09-01 20:09 – Updated: 2026-09-02 15:44

Title

Mail: Email address spoofing via malformed RFC 2047 encoded-words

Summary

Mail is an internet library for Ruby designed to handle email generation, parsing, and sending. Prior to 2.9.1, Mail::Utilities.q_value_decode and Mail::Utilities.b_value_decode used a single String#match and an overly greedy charset capture to decode only the first RFC 2047 encoded-word and mishandle surrounding or subsequent text. A crafted malformed encoded-word in an address display name or local part could cross ? delimiters and make decoded From, To, or Reply-To header values differ from the raw values inspected by a human reviewer or downstream parser, enabling apparent sender or recipient spoofing, phishing, or authorization-check bypass. This issue is fixed in version 2.9.1.

Severity

5.3 (Medium)


                        
                          CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-09-02 15:44 UTC

CWE

CWE-436 - Interpretation Conflict

Assigner

GitHub_M mitre root

References

4 references

URL	Tags
https://github.com/mikel/mail/security/advisories…	x_refsource_CONFIRM
https://github.com/mikel/mail/pull/1664	x_refsource_MISC
https://github.com/mikel/mail/commit/f9d59c2e447a…	x_refsource_MISC
https://github.com/mikel/mail/releases/tag/2.9.1	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version
mikel	mail	Affected: < 2.9.1

Show details on NVD website

JSON

To clipboard

{
  "containers": {
    "adp": [
      {
        "metrics": [
          {
            "other": {
              "content": {
                "id": "CVE-2026-63435",
                "options": [
                  {
                    "Exploitation": "none"
                  },
                  {
                    "Automatable": "yes"
                  },
                  {
                    "Technical Impact": "partial"
                  }
                ],
                "role": "CISA Coordinator",
                "timestamp": "2026-09-02T15:44:44.094469Z",
                "version": "2.0.3"
              },
              "type": "ssvc"
            }
          }
        ],
        "providerMetadata": {
          "dateUpdated": "2026-09-02T15:44:56.368Z",
          "orgId": "134c704f-9b21-4f2e-91b3-4a467353bcc0",
          "shortName": "CISA-ADP"
        },
        "title": "CISA ADP Vulnrichment"
      }
    ],
    "cna": {
      "affected": [
        {
          "product": "mail",
          "vendor": "mikel",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 2.9.1"
            }
          ]
        }
      ],
      "descriptions": [
        {
          "lang": "en",
          "value": "Mail is an internet library for Ruby designed to handle email generation, parsing, and sending. Prior to 2.9.1, Mail::Utilities.q_value_decode and Mail::Utilities.b_value_decode used a single String#match and an overly greedy charset capture to decode only the first RFC 2047 encoded-word and mishandle surrounding or subsequent text. A crafted malformed encoded-word in an address display name or local part could cross ? delimiters and make decoded From, To, or Reply-To header values differ from the raw values inspected by a human reviewer or downstream parser, enabling apparent sender or recipient spoofing, phishing, or authorization-check bypass. This issue is fixed in version 2.9.1."
        }
      ],
      "metrics": [
        {
          "cvssV3_1": {
            "attackComplexity": "LOW",
            "attackVector": "NETWORK",
            "availabilityImpact": "NONE",
            "baseScore": 5.3,
            "baseSeverity": "MEDIUM",
            "confidentialityImpact": "NONE",
            "integrityImpact": "LOW",
            "privilegesRequired": "NONE",
            "scope": "UNCHANGED",
            "userInteraction": "NONE",
            "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:N",
            "version": "3.1"
          }
        }
      ],
      "problemTypes": [
        {
          "descriptions": [
            {
              "cweId": "CWE-436",
              "description": "CWE-436: Interpretation Conflict",
              "lang": "en",
              "type": "CWE"
            }
          ]
        }
      ],
      "providerMetadata": {
        "dateUpdated": "2026-09-01T20:09:20.820Z",
        "orgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
        "shortName": "GitHub_M"
      },
      "references": [
        {
          "name": "https://github.com/mikel/mail/security/advisories/GHSA-mvxr-6m87-mv2q",
          "tags": [
            "x_refsource_CONFIRM"
          ],
          "url": "https://github.com/mikel/mail/security/advisories/GHSA-mvxr-6m87-mv2q"
        },
        {
          "name": "https://github.com/mikel/mail/pull/1664",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mikel/mail/pull/1664"
        },
        {
          "name": "https://github.com/mikel/mail/commit/f9d59c2e447af42e2c3dec5a56b1bb25c7292859",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mikel/mail/commit/f9d59c2e447af42e2c3dec5a56b1bb25c7292859"
        },
        {
          "name": "https://github.com/mikel/mail/releases/tag/2.9.1",
          "tags": [
            "x_refsource_MISC"
          ],
          "url": "https://github.com/mikel/mail/releases/tag/2.9.1"
        }
      ],
      "source": {
        "advisory": "GHSA-mvxr-6m87-mv2q",
        "discovery": "UNKNOWN"
      },
      "title": "Mail: Email address spoofing via malformed RFC 2047 encoded-words"
    }
  },
  "cveMetadata": {
    "assignerOrgId": "a0819718-46f1-4df5-94e2-005712e83aaa",
    "assignerShortName": "GitHub_M",
    "cveId": "CVE-2026-63435",
    "datePublished": "2026-09-01T20:09:20.820Z",
    "dateReserved": "2026-07-16T19:35:57.767Z",
    "dateUpdated": "2026-09-02T15:44:56.368Z",
    "state": "PUBLISHED"
  },
  "dataType": "CVE_RECORD",
  "dataVersion": "5.2"
}

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.

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.
Browse all ATT&CK techniques and the vulnerabilities related to each.

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Action not permitted

OESA-2026-4104 (CVE-2026-63435)

CVE-2026-63435 (GCVE-0-2026-63435)

Tags

Sightings

Nomenclature

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