Bun hosted and vendored rewiring rewrites bundled: true lock entries that Bun never fetches: the bundled copy stays unpatched, scan reports success, and vendored vex attests not_affected #469

[agent] Found by the scheduled Bun bug-hunt routine (ledger #306).

Summary

Bun records a package's bundleDependencies in bun.lock as their own entries, keyed parent/child and carrying { "bundled": true }:

"@bh/bund/is-number": ["[email protected]", "", { "bundled": true }, "sha512-…"],

Bun unpacks these from the parent's tarball and never fetches them. That's the same reason #325 / #337 made npm skip and contest inBundle copies. The Bun backends have no such handling:

1. Hosted (scan --mode hosted) rewrites the bundled entry to the Socket URL. It reports redirected: 1, status: success and no warning. npm emits redirect_npm_bundled_instance_skipped for the same shape.
2. Vendored (scan --mode vendored) rewrites it to .socket/vendor/npm/<uuid>/…tgz, also silently.
3. After a fresh bun install --frozen-lockfile, the copy the parent actually loads (node_modules/<parent>/node_modules/<pkg>) is unpatched. On text locks with Bun ≥ 1.2, Bun also hoists an extra, patched top-level copy from the rewritten entry, which nothing requires.
4. Vendored vex (default, with verification) attests not_affected for that purl on every Bun version and lock format. On Bun 1.1.45 and on bun.lockb there is no patched copy anywhere on disk. Hosted vex --no-verify attests too, although --no-verify must skip only the hashing, never the wiring/contest gates. Hosted default vex does refuse (not_applied), because its installed-tree check sees the bundled copy.

vex/discover/bun.rs and both Bun rewriters never look at bundled (grep -n bundled returns nothing in any *bun* source file).

Impact

A project whose dependency bundles a vulnerable package gets a successful hosted/vendored run and, in vendored mode, a verified OpenVEX not_affected statement, while the code that actually runs is the unpatched bundled copy. It's the Bun twin of #325, which was fixed for npm only.

Repro (Linux, any Bun ≥ 1.1.39; mock patch API, no secrets)

Fixture: a scoped package @bh/[email protected] with "bundleDependencies": ["is-number"], shipping node_modules/is-number (7.0.0) inside its tarball, served from a local registry scope. A mock patch API serves a hosted/vendored patch for pkg:npm/[email protected] that prepends /* SOCKET-PATCHED */ to index.js. The routes are the same ones e2e_redirect_bun_build.rs mocks: patches/batch, by-package, patches/package, view/<uuid>, plus the hosted tarball.

mkdir p && cd p
echo '{"name":"p","version":"1.0.0","dependencies":{"@bh/bund":"1.0.0"}}' > package.json
printf '[install.scopes]\n"@bh" = "http://127.0.0.1:18765/npm/"\n' > bunfig.toml
bun install                                  # bun.lock gets "@bh/bund/is-number": [..., {"bundled": true}, ...]
export SOCKET_PATCH_SERVER_URL=http://127.0.0.1:18765
G="--api-url http://127.0.0.1:18765 --org org --api-token fake"
socket-patch scan --mode vendored --json --yes --cwd . $G   # status success, no warnings
grep bundled bun.lock
#  "@bh/bund/is-number": ["[email protected]/vendor/npm/<uuid>/is-number-7.0.0.tgz", { "bundled": true }, "sha512-<patched>"],
# fresh checkout, cold cache
rm -rf node_modules && BUN_INSTALL_CACHE_DIR=$(mktemp -d) bun install --frozen-lockfile    # exit 0
grep -c SOCKET-PATCHED node_modules/@bh/bund/node_modules/is-number/index.js            # 0  <- the copy @bh/bund loads
node -e 'const p=require.resolve("is-number",{paths:[require("path").dirname(require.resolve("@bh/bund"))]});console.log(p)'
#   …/node_modules/@bh/bund/node_modules/is-number/index.js  (unpatched)
socket-patch vex --cwd . --json $G -O out.vex.json; echo $?   # 0, event "verified", statement not_affected

Hosted is the same with --mode hosted: redirected: 1, no warning, the bundled copy unpatched after the frozen install, and vex --no-verify exits 0 with not_affected.

Expected vs actual

• Expected: CLI_CONTRACT.md, "Contested locks": "A bundled npm copy … of the same name@version contests the reference … npm unpacks it from the parent package's tarball, so no rewire reaches it and it stays unpatched." Bun's bundled: true entry has exactly those semantics. So the rewriters should skip it with a warning (like redirect_npm_bundled_instance_skipped / vendor_bundled_instance_skipped), or refuse like vlt's vendor_bundled_deps_unsupported. VEX should report patched_ref_unattributable and not attest, including under --no-verify (the contract's "Liveness gates": --no-verify skips only the hashing).
• Actual: the bundled entry is rewired silently, the run succeeds, and vendored vex (verified) and hosted vex --no-verify both attest not_affected while the loaded copy is unpatched.

Matrix (Linux; real Bun from npm @oven/bun-linux-x64; main d984832; shape: bundled copy only)

Each 1.4.2 text cell reproduced on 2+ fresh runs. The "both" shape (the project also depends on [email protected] directly) gives the same result: both entries are rewired, and the bundled copy stays unpatched. macOS and Windows weren't probed. The behaviour is in lockfile parsing and rewriting, which isn't OS-specific.

First bad version: not a regression. Release 4.0.0 behaves the same, and also attests in hosted default vex.

Suspect code

• crates/socket-patch-core/src/patch/redirect/mod.rs:3633 (rewrite_bun_lock entry loop: matches on the spec only, not the {meta}.bundled flag)
• crates/socket-patch-core/src/vendor/bun_lock.rs:285 / :1013 (vendored text rewrite)
• crates/socket-patch-core/src/patch/redirect/bun_binary.rs:18, crates/socket-patch-core/src/vendor/bun_binary.rs:25 (binary lock: the bundled record is rewritten too)
• crates/socket-patch-core/src/vex/discover/bun.rs:119 (discovery takes the bundled entry as a live Socket ref, and has no bundled contest like vex/discover/npm.rs got in Fix npm VEX attesting packages with an unpatched bundled copy (#325) #337)

Related: #325 (npm, fixed by #337), #405 (another Bun VEX false attestation).