GHSA-gmc6-fwg3-75m5: MimeKit

Package	Ecosystem	Affected	Fixed in
MimeKit	NuGet	>=3.0.0, <4.7.1	4.7.1

Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

MimeKit versions 3.0.0 up to 4.7.0 are vulnerable to denial of service through a vulnerable transitive dependency. The source gives few details on the flaw itself. An attacker could trigger it by sending S/MIME messages for decryption or verification, or by supplying third-party X.509 certificates for encrypting outgoing messages. Upgrade MimeKit to 4.7.1 or later.

Written 9 Nov 2026.

Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

Severity and exploitation

Score	Rating	CVSS	Vector	Source
7.5	High	3.1	CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H	GitHub Advisory Database

CISA KEV Not listed.
EPSS No score.

Timeline

31 Oct 2026, 15:23 UTC First seen by agentprime
31 Oct 2026, 15:23 UTC Confirmed by OSV

Sources

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.