CVE-2026-63435

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.

Database specific

{
    "cna_assigner": "GitHub_M",
    "cwe_ids": [
        "CWE-436"
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/63xxx/CVE-2026-63435.json"
}

References

Affected packages

Git / github.com/mikel/mail

Affected ranges

Type

GIT

Repo

https://github.com/mikel/mail

Events

Introduced

Fixed

d645d7b5b7d03218b0bc8971ef041c991a63f5f7

Fixed

f9d59c2e447af42e2c3dec5a56b1bb25c7292859

Database specific

Show details

{
    "extracted_events": [
        {
            "range": [
                {
                    "introduced": "0"
                },
                {
                    "fixed": "2.9.1"
                }
            ],
            "source": "AFFECTED_FIELD",
            "strategy": "StringRangeExpression"
        },
        {
            "range": [
                {
                    "fixed": "f9d59c2e447af42e2c3dec5a56b1bb25c7292859"
                }
            ],
            "source": "REFERENCES_COMMIT"
        },
        {
            "original_tag": "2.9.1",
            "range": [
                {
                    "fixed": "d645d7b5b7d03218b0bc8971ef041c991a63f5f7"
                }
            ],
            "source": "REFERENCES_TAG"
        }
    ]
}

Affected versions

2.*

2.0.3

2.0.5

2.1.2

2.1.3

2.2.0

2.2.10

2.2.11

2.2.13

2.2.14

2.2.15

2.2.17

2.2.18

2.2.2

2.2.3

2.2.4

2.2.5

2.2.5.1

2.2.5.2

2.2.6

2.2.8

2.2.9

2.3.0

2.4.1

2.4.2

2.4.3

2.4.4

2.5.0

2.5.1

2.5.2

2.5.3

2.6.0

2.6.1

2.6.3

2.6.4

2.7.0

2.7.0.rc1

2.7.0.rc2

2.7.0.rc3

Database specific

source

"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/CVE-2026-63435.json"