Glob: AbortSignal cancellation bypass allows post-timeout filesystem traversal

Summary

In glob 13.0.6, an aborted async walk rejects or emits an error but continues recursively reading directories in the background.

The root cause is that abort branches in src/walker.ts call cb() without returning. As a result, callers that rely on signal or AbortSignal.timeout() to bound glob traversal cost can still incur filesystem I/O and CPU work after the request has already been rejected.

Details

This was reproduced on glob v13.0.6 (commit e80cb38ae60d6cbff9e75f39032a994858994d35).

The README documents that the signal option cancels the glob walk. However, in src/walker.ts, the following methods call cb() when this.signal?.aborted is true but do not return:

• GlobUtil.walkCB()
• GlobUtil.walkCB2()
• GlobUtil.walkCBSync()
• GlobUtil.walkCB2Sync()

Example vulnerable pattern:

if (this.signal?.aborted) cb()

Because execution continues after cb(), the walker still reaches processor.processPatterns(), readdirCB(), and recursive walkCB2() calls.

The issue was directly demonstrated against v13.0.6. A source-history review shows the same missing-return pattern is present in tagged releases from v9.0.0 through v13.0.6.

The issue affects both glob() and globStream().

Recommended fix: Change each abort branch to return immediately:

if (this.signal?.aborted) return cb()

Proof of concept

Environment:

• Linux x86_64
• Node.js v22.23.3
• npm 10.9.9
• glob 13.0.6

Reproduction steps:

1. Install the affected package: npm init -y npm install [email protected]

2. Run the attached PoC: node poc/abort-continues-work.mjs

The PoC aborts after the first readdir() call, waits briefly, and counts how many more directory reads happen after the promise has already rejected.

Observed output on the vulnerable version:

{ "rejection": "Error: probe-abort", "readdirCalls": 1365, "readdirCallsAtReject": 5, "readdirCallsAfterReject": 1360 }

Expected behavior: readdirCallsAfterReject should be 0.

A second PoC using AbortSignal.timeout() also reproduces the issue:

{ "rejection": "TimeoutError: The operation was aborted due to timeout", "readdirCalls": 133, "readdirCallsAtReject": 1, "readdirCallsAfterReject": 132 }

The same test against a patched build with return cb() in the four abort branches stops immediately:

{ "readdirCalls": 1, "readdirCallsAtReject": 1, "readdirCallsAfterReject": 0 }

Impact

This is an availability issue.

Applications that expose globbing over attacker-influenced patterns or attacker-controlled directory trees and use AbortSignal / AbortSignal.timeout() as a traversal budget can still perform significant filesystem I/O and CPU work after a request has already timed out or been canceled.

Repeated timed-out requests can stack background glob walks and degrade worker throughput or service availability.

No confidentiality or integrity impact was observed.