[AutoPR- Security] Patch rsync for CVE-2026-18743 [LOW]

[Azure Linux Security Servicing Account (azurelinux-security)]

Auto Patch rsync for CVE-2026-18743.

Autosec pipeline run -> https://dev.azure.com/mariner-org/mariner/_build/results?buildId=1198192&view=results

CVE-2026-18743 : Single Patch Backporter Pipeline Run -> https://dev.azure.com/mariner-org/mariner/_build/results?buildId=1198195&view=results

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

What does the PR accomplish, why was it needed?

• Auto Patch rsync for CVE-2026-18743 (LOW).

Change Log

• CVE-2026-18743

Does this affect the toolchain?

YES/NO

Associated issues

• N/A

Links to CVEs

• https://nvd.nist.gov/vuln/detail/CVE-2026-18743

Test Methodology

• Pipeline build id: Buddy Build URL

[azure-pipelines]

Azure Pipelines:
There may be pipelines that require an authorized user to comment /azp run to run.

[durgajagadeesh]

Changes summary for CVE-2026-18743 fix in rsync-3.5.0:

1. AI patch includes Upstream patch reference.

2. This CVE is affected because our popt source code(v1.6) falls below v1.19

3. Backported: Yes

4. The AI patch is incomplete with the upstream patch.
   5 . CVE-2026-18743.patch — The original AI-generated backport was incomplete and would not compile. It removed the size_t t variable but left 4 references to t intact, and critically did not fix the actual vulnerability — the flawed maxargvlen reallocation logic ((t > maxargvlen) ? t*2 : maxargvlen*2). The corrected patch now matches upstream commit 3de3d3a from popt PR #137, making all 6 required line changes across both vulnerable code paths in poptConfigFileToString().

5. rsync.spec — Added -p1 to %autosetup because the patch uses git-format diff paths (a/popt/poptparse.c). Without -p1, RPM's patch invocation cannot strip the a/ prefix and fails with "No file to patch."

6. Upstream test files skipped — The upstream PR Use Clear Linux optimized packages #137 includes 4 commits; only commit 4/4 (3de3d3a) is the actual CVE fix. Commits 1–3 fix test memory leaks and enable ASAN/UBSAN in popt's own CI, and commit 4 adds popt-specific test data (tests/test3-data/05.input, tests/test3-data/05.answer, tests/testit.sh). These are excluded because:

   • They belong to popt's standalone test suite (test3 binary), which rsync does not build or ship
   • rsync's bundled popt copy has no tests/ directory — the files would have nowhere to go
   • The fix was independently verified against the upstream PoC and 14 additional test vectors in a Docker container using the built RPM, confirming both vulnerable reallocation paths are fixed

7. Buddy build:

8. The patch is applying cleanly.

[jykanase]

• Buddy Build passed.
• Patch matches with upstream patch.
• Patch applied during the build (check rpm.log).
• Patch include an upstream reference.