Angular: XSRF Token Leakage via URL Parsing Discrepancy in Angular HTTP Client (Incomplete fix for CVE-2025-66035)

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No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.34 and 21.0.3, the @angular/common HttpClient function xsrfInterceptorFn uses a regular expression that does not normalize request URLs in the same way as the browser's WHATWG URL parser. With XSRF protection enabled, a mutating HTTP request to an attacker-controlled URL containing backslashes, stripped control characters or spaces, or removable ASCII whitespace can be misclassified as relative and same-origin, causing the interceptor to attach the X-XSRF-TOKEN header before the browser dispatches the request to a cross-origin host. With permissive CORS handling for the custom header, the attacker can obtain the victim's XSRF token and use it to perform cross-site request forgery against the victim session. This issue is fixed in versions 20.3.34 and 21.0.3.

Source published

5 Nov 2026 20:25:07 UTC

Source modified

5 Nov 2026 20:25:07 UTC

Observed here

5 Nov 2026 21:36:21 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · 5.9 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.34 and 21.0.3, the @angular/common HttpClient function xsrfInterceptorFn uses a regular expression that does not normalize request URLs in the same way as the browser's WHATWG URL parser. With XSRF protection enabled, a mutating HTTP request to an attacker-controlled URL containing backslashes, stripped control characters or spaces, or removable ASCII whitespace can be misclassified as relative and same-origin, causing the interceptor to attach the X-XSRF-TOKEN header before the browser dispatches the request to a cross-origin host. With permissive CORS handling for the custom header, the attacker can obtain the victim's XSRF token and use it to perform cross-site request forgery against the victim session. This issue is fixed in versions 20.3.34 and 21.0.3.

Source published

Nov 5, 2026, 8:25:07 PM (timezone not stated)

Source modified

Nov 5, 2026, 8:25:07 PM (timezone not stated)

Observed here

7 Nov 2026 04:32:44 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 4.0 · 5.9 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Angular is a development platform for building mobile and desktop web applications using TypeScript/JavaScript and other languages. Prior to 20.3.34 and 21.0.3, the @angular/common HttpClient function xsrfInterceptorFn uses a regular expression that does not normalize request URLs in the same way as the browser's WHATWG URL parser. With XSRF protection enabled, a mutating HTTP request to an attacker-controlled URL containing backslashes, stripped control characters or spaces, or removable ASCII whitespace can be misclassified as relative and same-origin, causing the interceptor to attach the X-XSRF-TOKEN header before the browser dispatches the request to a cross-origin host. With permissive CORS handling for the custom header, the attacker can obtain the victim's XSRF token and use it to perform cross-site request forgery against the victim session. This issue is fixed in versions 20.3.34 and 21.0.3.

Source published

5 Nov 2026 21:18:35 UTC

Source modified

5 Nov 2026 21:18:35 UTC

Observed here

6 Nov 2026 09:36:27 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 4.0 · [email protected] · Secondary · 5.9 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

An incomplete fix for [GHSA-58c5-g7wp-6w37](https://github.com/angular/angular/security/advisories/GHSA-58c5-g7wp-6w37) (`CVE-2025-66035`) in `@angular/common`'s HTTP Client (`HttpClient`) allows Cross-Site Request Forgery (XSRF) tokens to be leaked to attacker-controlled cross-origin domains when requests use URLs that exploit parsing discrepancies between regular expressions and the browser's WHATWG URL parser. ### Technical Description To address `CVE-2025-66035`, `xsrfInterceptorFn` introduced a regular expression (`const ABSOLUTE_URL_REGEX = /^(?:https?:)?\/\//i`) to detect and skip absolute and protocol-relative URLs before attaching the `X-XSRF-TOKEN` header. However, browsers resolve request URLs passed to `fetch()` and `XMLHttpRequest.open()` using the **WHATWG URL parser**. For `http:` and `https:` schemes, the WHATWG URL standard performs several normalizations prior to resolving the authority/origin: * Backslashes (`\`) are treated as forward slashes (`/`) — e.g., `/\evil.example/x`, `\\evil.example/x`, `\/evil.example/x`, `https:\\evil.example/x`, `https:/\evil.example/x`. * Leading and trailing C0 control characters and spaces (`<= 0x20`) are stripped — e.g., `' //evil.example/x'`, `'\0//evil.example/x'`, `'\x1f//evil.example/x'`. * ASCII tab (`\t`), newline (`\n`), and carriage return (`\r`) characters are removed anywhere in the input — e.g., `'/\t/evil.example/x'`, `'/\n/evil.example/x'`, `'htt\tps://evil.example/x'`. Because these URLs do not match `/^(?:https?:)?\/\//i`, `xsrfInterceptorFn` treats them as relative same-origin URLs and attaches the `X-XSRF-TOKEN` header, while the browser resolves and dispatches the request to the cross-origin host (`evil.example`). Note: Angular `21.0.3+` and `22.x` replaced the regular expression with a WHATWG `new URL(req.url, locationOrigin)` origin comparison in [#65683](https://github.com/angular/angular/pull/65683) and were already unaffected. However, the `20.3.x` LTS branch retained the regular expression until `20.3.34`. ### Impact The token leakage bypasses Angular's built-in XSRF protection on affected versions, allowing an attacker to capture the user's valid `X-XSRF-TOKEN` header if their server permits the request and custom header via CORS. Once obtained, the attacker can perform Cross-Site Request Forgery (CSRF) attacks against the victim user's session. ### Attack Preconditions 1. The victim's Angular application must have **XSRF protection enabled** (enabled by default in `HttpClient`). 2. The attacker must be able to make the application send a state-changing HTTP request (e.g., `POST`, `PUT`, `DELETE`, `PATCH`) to a URL they control (such as `/\attacker.example/api` or ` //attacker.example/api`). ### Patches The issue is resolved by parsing and comparing the request URL's origin against the application's current origin using the standard `URL` constructor (`new URL(req.url, locationOrigin)`). * `21.0.3` (and all `22.x` releases) * `20.3.34` ### Workarounds If you cannot immediately upgrade to a patched version: * Validate and normalize outgoing request URLs using `new URL(url, window.location.origin)` and verify that `parsedUrl.origin === window.location.origin` before passing dynamic URLs to mutating `HttpClient` requests. * Avoid passing untrusted or user-controlled URLs to `HttpClient` mutating methods.

Source published

20 Oct 2026 20:37:57 UTC

Source modified

20 Oct 2026 20:45:05 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

Original source record · Cite this exact observation · Complete original publisher JSON

This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V4 · CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:A/VC:H/VI:N/VA:N/SC:N/SI:N/SA:N

Publisher rating · MODERATE