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Improve error message when Origin header is invalid #14743

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brophdawg11 merged 5 commits into from
Jan 23, 2026
+38 −4
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Improve error message when Origin header is invalid #14743

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590a38b
better error messaging when Origin header is malformed
rossipedia Jan 23, 2026
d311c82
changeset
rossipedia Jan 23, 2026
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brophdawg11 Jan 23, 2026
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Add test
brophdawg11 Jan 23, 2026
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brophdawg11 Jan 23, 2026
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5 changes: 5 additions & 0 deletions .changeset/hot-jokes-allow.md
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Original file line number Diff line number Diff line change
@@ -0,0 +1,5 @@
---
"react-router": patch
---

Improve error message when Origin header is invalid
17 changes: 13 additions & 4 deletions packages/react-router/lib/actions.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -3,10 +3,19 @@ export function throwIfPotentialCSRFAttack(
allowedActionOrigins: string[] | undefined,
) {
let originHeader = headers.get("origin");
let originDomain =
typeof originHeader === "string" && originHeader !== "null"
? new URL(originHeader).host
: originHeader;
let originDomain: string | null = null;

try {
originDomain =
typeof originHeader === "string" && originHeader !== "null"
? new URL(originHeader).host
: originHeader;
} catch {
// error parsing the Origin header as a valid URL
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throw new Error(
`provided \`origin\` header is not a valid URL. Aborting the action.`,
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);
}
let host = parseHostHeader(headers);

if (originDomain && (!host || originDomain !== host.value)) {
Expand Down