| Title | The Trusted Domain Project OpenDKIM 2.11.0 Out-of-Bounds Read |
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| Description | OpenDKIM contains an off-by-one error in the decoder for the DKIM sender-identity field. A crafted encoded identity can cause the decoder to overwrite the terminating null byte of a fixed-size stack buffer. Subsequent string processing may then read beyond the end of the buffer.
The issue is triggered while processing an inbound message containing a DKIM signature and occurs before cryptographic verification, so a valid signature or authentication is not required. A remote attacker may cause the mail-filtering process to crash, resulting in denial of service. Reading adjacent stack data may also create a limited potential information-disclosure condition, although disclosure has not been demonstrated.
dkim_qp_decode() uses an inclusive comparison when checking the output position against the caller-provided buffer limit. This permits one byte to be written beyond the intended decoded-data boundary, overwriting the null terminator. The caller subsequently treats the buffer as a null-terminated string and may read past its end while processing the decoded identity. |
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| Source | ⚠️ https://weitongli.com/share/opendkim-qp-off-by-one.html |
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| User | WeitongLi (UID 100239) |
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| Submission | 08/06/2026 09:32 (2 months ago) |
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| Moderation | 09/27/2026 09:36 (2 months later) |
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| Status | Accepted |
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| VulDB entry | 410839 [Trusted Domain Project OpenDKIM up to 2.11.0 Decoder util.c dkim_qp_decode off-by-one] |
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| Points | 20 |
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