GHSA-gmc6-fwg3-75m5 is a high-severity (CVSS 7.5) vulnerability in MimeKit. A fix is available for MimeKit — see the affected versions and patch details below.
Mimekit has vulnerable dependency that can lead to denial of service
Real-World Exposure
MimeKitReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects NuGet packages — download data is not available via public APIs for these ecosystems.
Description
Summary
Denial of service vulnerability.
Details
See: https://github.com/advisories/GHSA-447r-wph3-92pm and https://github.com/dotnet/announcements/issues/312
PoC
Update System.Security.Cryptography.Pkcs to 8.0.1 so that the transitive dependency with the issue gets updated
Impact
Denial of service vulnerability. Affects MimeKit (>= v3.0.0 and <= v4.7.0) when used to decrypt or verify incoming S/MIME messages as well as importing 3rd-party X.509 certificates for use with encrypting outgoing S/MIME messages.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| .NETNuGet | MimeKit | ≥ 3.0.0&&< 4.7.1 | 4.7.1dotnet add package MimeKit --version 4.7.1 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for MimeKit, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update MimeKit to 4.7.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-gmc6-fwg3-75m5 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like GHSA-gmc6-fwg3-75m5 can be triaged on real exposure rather than presence alone.
Tailored to GHSA-gmc6-fwg3-75m5. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-gmc6-fwg3-75m5 in your dependencies?
O3 Security finds GHSA-gmc6-fwg3-75m5 across NuGet dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.