fix: prevent SSRF via /cors endpoint by blocking private/reserved IPs#4084
Merged
khassel merged 1 commit intoMagicMirrorOrg:developfrom Apr 3, 2026
Merged
fix: prevent SSRF via /cors endpoint by blocking private/reserved IPs#4084khassel merged 1 commit intoMagicMirrorOrg:developfrom
khassel merged 1 commit intoMagicMirrorOrg:developfrom
Conversation
Resolve target hostname before proxying and reject any address that is not globally routable (loopback, RFC 1918, link-local, etc.) using ipaddr.js and dns.lookup().
khassel
approved these changes
Apr 3, 2026
khassel
pushed a commit
that referenced
this pull request
Apr 4, 2026
PR #4084 blocked SSRF by checking the IP before `fetch()` — but `fetch()` resolves DNS again on its own. With DNS rebinding (TTL=0, alternating IPs) an attacker can slip a private IP through between check and connection. Fix: resolve DNS once, validate, pin the validated IP for the connection. No second DNS query → no rebinding window. `isPrivateTarget()` is gone, code is shorter than before. Not a likely attack for a typical MagicMirror setup, but it doesn't add complexity so there's no reason not to close the gap.
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Resolve target hostname before proxying and reject any address that is not globally routable (loopback, RFC 1918, link-local, etc.) using ipaddr.js and dns.lookup().