Impact
The V8 inspector intentionally allows arbitrary code execution within the Workers sandbox for debugging. wrangler dev would previously start an inspector server listening on all network interfaces. This would allow an attacker on the local network to connect to the inspector and run arbitrary code. Additionally, the inspector server did not validate Origin/Host headers, granting an attacker that can trick any user on the local network into opening a malicious website the ability to run code. If wrangler dev --remote was being used, an attacker could access production resources if they were bound to the worker.
Patches
This issue was fixed in wrangler@3.19.0 and wrangler@2.20.2. Whilst wrangler dev's inspector server listens on local interfaces by default as of wrangler@3.16.0, an SSRF vulnerability in miniflare allowed access from the local network until wrangler@3.18.0. wrangler@3.19.0 and wrangler@2.20.2 introduced validation for the Origin/Host headers.
Workarounds
Unfortunately, Wrangler doesn't provide any configuration for which host that inspector server should listen on. Please upgrade to at least wrangler@3.16.0, and configure Wrangler to listen on local interfaces instead with wrangler dev --ip 127.0.0.1 to prevent SSRF. This removes the local network as an attack vector, but does not prevent an attack from visiting a malicious website.
References
Lekensteyn Reporter
Impact
The V8 inspector intentionally allows arbitrary code execution within the Workers sandbox for debugging.
wrangler devwould previously start an inspector server listening on all network interfaces. This would allow an attacker on the local network to connect to the inspector and run arbitrary code. Additionally, the inspector server did not validateOrigin/Hostheaders, granting an attacker that can trick any user on the local network into opening a malicious website the ability to run code. Ifwrangler dev --remotewas being used, an attacker could access production resources if they were bound to the worker.Patches
This issue was fixed in
wrangler@3.19.0andwrangler@2.20.2. Whilstwrangler dev's inspector server listens on local interfaces by default as ofwrangler@3.16.0, an SSRF vulnerability inminiflareallowed access from the local network untilwrangler@3.18.0.wrangler@3.19.0andwrangler@2.20.2introduced validation for theOrigin/Hostheaders.Workarounds
Unfortunately, Wrangler doesn't provide any configuration for which host that inspector server should listen on. Please upgrade to at least
wrangler@3.16.0, and configure Wrangler to listen on local interfaces instead withwrangler dev --ip 127.0.0.1to prevent SSRF. This removes the local network as an attack vector, but does not prevent an attack from visiting a malicious website.References