[CRITICAL] Patch moby-containerd-cc for CVE-2026-39821

[akhila-guruju]

Merge Checklist

All boxes should be checked before merging the PR (just tick any boxes which don't apply to this PR)

• The toolchain has been rebuilt successfully (or no changes were made to it)
• The toolchain/worker package manifests are up-to-date
• Any updated packages successfully build (or no packages were changed)
• Packages depending on static components modified in this PR (Golang, *-static subpackages, etc.) have had their Release tag incremented.
• Package tests (%check section) have been verified with RUN_CHECK=y for existing SPEC files, or added to new SPEC files
• All package sources are available
• cgmanifest files are up-to-date and sorted (./cgmanifest.json, ./toolkit/scripts/toolchain/cgmanifest.json, .github/workflows/cgmanifest.json)
• LICENSE-MAP files are up-to-date (./LICENSES-AND-NOTICES/SPECS/data/licenses.json, ./LICENSES-AND-NOTICES/SPECS/LICENSES-MAP.md, ./LICENSES-AND-NOTICES/SPECS/LICENSE-EXCEPTIONS.PHOTON)
• All source files have up-to-date hashes in the *.signatures.json files
• sudo make go-tidy-all and sudo make go-test-coverage pass
• Documentation has been updated to match any changes to the build system
• Ready to merge

---

Summary

Patch moby-containerd-cc for CVE-2026-39821

Change Log

• new file: SPECS/moby-containerd-cc/CVE-2026-39821.patch
• modified: SPECS/moby-containerd-cc/moby-containerd-cc.spec

Does this affect the toolchain?

YES/NO

Associated issues

• #xxxx

Links to CVEs

• https://nvd.nist.gov/vuln/detail/CVE-2026-39821

Test Methodology

• Local Build

[Kanishk-Bansal]

/azurepipelines run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[CBL-Mariner-Bot]

Auto cherry-pick results:

• 3.0-dev ✅ -> [AUTO-CHERRYPICK] [CRITICAL] Patch moby-containerd-cc for CVE-2026-39821 - branch 3.0-dev #17570

Auto cherry-pick pipeline run -> https://dev.azure.com/mariner-org/mariner/_build/results?buildId=1129632&view=results