GHSA-hhg7-c65m-h7ff / CVE-2026-45753
この脆弱性で確認すること
- 対象製品
- symfony/html-sanitizer / symfony/symfony
- WATRIXで確認できる範囲
- 利用製品・バージョン・設定を確認し、影響調査や対策の進め方をご相談いただけます。掲載だけで自動診断や復旧の対応を保証するものではありません。
- 情報の作成方法
- 収集した原典情報
情報整理：WATRIX合同会社。影響の確定や侵害の有無は、実際の版・設定・ログ等を確認して判断します。
- CVSS
- 1.2
- 公開元の公表日時
- 2026/05/29 1:43
- 公開元の更新日時
- 2026/05/29 1:43
- 当サイトの収集処理
- 2026/11/07 0:00
原典の説明
公開元の記載です。日本語での確認手順・対処の解説が付いていない項目も含まれます。
Symfony's HtmlSanitizer UrlAttributeSanitizer Omits action/formaction/poster/cite — `javascript`: URI Survives Sanitization (XSS)
### Description `symfony/html-sanitizer` lets applications sanitise untrusted HTML. `UrlAttributeSanitizer` is the visitor responsible for validating URL-valued attributes and stripping dangerous schemes from them; it runs on every element regardless of configuration. Whether an attribute is *kept* is decided by the element/attribute allow-list; validating the *scheme* of a URL attribute is solely `UrlAttributeSanitizer`'s responsibility. `UrlAttributeSanitizer::getSupportedAttributes()` returned only `['src', 'href', 'lowsrc', 'background', 'ping']`. The HTML URL-valued attributes `action` (`<form>`), `formaction` (`<button>`, `<input type=image>`), `poster` (`<video>`) and `cite` (`<blockquote>`, `<q>`, `<del>`, `<ins>`) were missing from that list, so `DomVisitor` never invoked scheme validation for them. As a result, when a configuration admits one of those attributes, a `javascript:` URI in it survived sanitisation. ### Conditions for exploitation `allowSafeElements()` is **not** affected: `<form>` and the `formaction` attribute are both flagged unsafe in `W3CReference`, and `allowElement('form')` resets the element's attribute list. Reaching the vulnerable attributes requires a deliberately permissive configuration, for example: * `<form>` + `action`: `allowElement('form', '*')`, `allowElement('form', ['action', …])`, `allowElement('form')->allowAttribute('action', 'form')`, or the `allowStaticElements()` preset (whose docblock already warns the output "may still contain other dangerous behaviors"); * `<button>` / `<input type=image>` + `formaction`: `allowElement(…, '*')`, `allowAttribute('formaction', …)`, or `allowStaticElements()`; * `<blockquote>` / `<q>` / `<del>` / `<ins>` + `cite`, or `<video>` + `poster`: similarly via `'*'`, `allowAttribute()`, or `allowStaticElements()`. For the `action` / `formaction` cases the victim must additionally submit the form or click the button. ### Resolution `UrlAttributeSanitizer` now also handles `action`, `formaction`, `cite` and `poster`. `action` / `formaction` / `cite` are validated against the link schemes (like `<a href>`, so `javascript:` is rejected and `data:` is dropped too); `poster` is validated against the media schemes (so `data:` images keep working). The behaviour of `<a href>` and `<img src>` is unchanged. One behaviour change to be aware of: a relative `action="/submit"` on an allowed `<form>` is now dropped by default (the same as `<a href>` / `<img src>` today); `->allowRelativeLinks()` re-enables it. The patch for this issue is available [here](https://github.com/symfony/symfony/commit/26a598fcfc4f903cc55ff202f642ee621839825e) for branch 6.4. ### Credits Symfony would like to thank Himanshu Anand and Rémi Pelloux for reporting the issue and Nicolas Grekas for providing the fix.
出典・著作権・ライセンスを確認する
- 出典
GitHub Advisory Database
- 利用許諾
CC-BY-4.0
- 利用条件
当サイトでの保存履歴
当サイトが取得した原本の履歴です。公開元での過去の改訂日時とは異なります。
初回保存のみです。訂正前の版はまだありません。
現在の保存内容2026/10/31 17:00
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