fix: prevent hang in restoreConfigFromBase on repos with .gitmodules by qozle · Pull Request #1166 · anthropics/claude-code-action

qozle · 2026-04-05T00:03:48Z

Problem

restoreConfigFromBase hangs indefinitely (users report ~4 hours) on repositories that have a .gitmodules file in the PR head. Fixes #1088.

Root cause: git fetch origin <base> --depth=1 reads .gitmodules from the working tree when fetch.recurseSubmodules=on-demand is set (the git default). The PR head's .gitmodules is attacker-controlled and present in the working directory at the time of the fetch. Git attempts to fetch submodule objects, which blocks waiting for credentials that never arrive in CI.

Fix

Two changes, both defence-in-depth:

1. Delete SENSITIVE_PATHS before fetching (order swap)

The attacker-controlled .gitmodules is removed before the git fetch call. Git never sees a submodule config to follow, regardless of runner git settings.

2. Pass --no-recurse-submodules to git fetch

Explicitly suppresses submodule fetching independent of any fetch.recurseSubmodules config on the runner.

The original order (fetch-then-delete) had a brief window where .gitmodules from the PR head could influence the fetch. The reorder also tightens the security property: if the subsequent git checkout fails for a path, the attacker-controlled file is already gone rather than present during the network operation.

Testing

bun test — 653 pass, 0 fail. No logic changes to the restore flow; the fix is purely ordering + flag.

When a PR head contains `.gitmodules`, git's default `fetch.recurseSubmodules=on-demand` config causes `git fetch` to attempt submodule object fetches. In CI (no credentials), this blocks indefinitely waiting for auth — producing ~4-hour hangs reported in anthropics#1088. Two changes, both defence-in-depth: 1. Delete SENSITIVE_PATHS *before* fetching. The attacker-controlled `.gitmodules` is absent during the network operation, so git never sees a submodule config to follow regardless of git settings. 2. Pass `--no-recurse-submodules` to the fetch. Suppresses submodule fetching explicitly, independent of any git config on the runner. The original order (fetch-then-delete) was a brief window where `.gitmodules` from the PR head could influence the fetch. Reordering also tightens the security property: if `git checkout` below fails, the attacker-controlled file is already gone rather than present during fetch. Fixes anthropics#1088. Co-Authored-By: Claude Sonnet 4.6 <[email protected]>

ashwin-ant approved these changes Apr 5, 2026

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ashwin-ant merged commit f328a5c into anthropics:main Apr 5, 2026
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fix: prevent hang in restoreConfigFromBase on repos with .gitmodules#1166

fix: prevent hang in restoreConfigFromBase on repos with .gitmodules#1166
ashwin-ant merged 1 commit intoanthropics:mainfrom
qozle:fix/restore-config-gitmodules-hang

qozle commented Apr 5, 2026

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qozle commented Apr 5, 2026

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