{"id":"CVE-2026-49212","aliases":["GHSA-34w5-c283-j9fg"],"url":"https://o3.security/vulnerability/CVE-2026-49212","summary":"Symfony UX: LiveComponentHydrator HMAC checksum lacks component and slot binding","details":"### Description\n\nIn `symfony/ux-live-component`, a component's server-side state is exposed to the browser as a set of props (`#[LiveProp]`-annotated properties). Props marked `writable: true` can be freely changed by the client. Read-only props are round-tripped to the browser and back, and their integrity is protected by an HMAC so the client cannot tamper with them. Child components additionally receive a `propsFromParent` blob, also HMAC-signed.\n\nThe HMAC computed by `Symfony\\UX\\LiveComponent\\LiveComponentHydrator` covered only the sorted prop key/value pairs. It didn't include the component name, the slot identifier (`props` vs `propsFromParent`), or any request context, and a single application-wide secret is used for every component. A signed blob the server minted for component A is therefore a valid signature for component B if the key names happen to match, and a `props` blob can be replayed in the `propsFromParent` slot (or the reverse). An attacker can use this to set a read-only prop on a target component to a value they were only ever allowed to choose as a writable prop on another component.\n\n### Resolution\n\nThe HMAC is now bound to its context: the component name and a slot identifier are included in the pre-image before hashing. Two constants (`CHECKSUM_SLOT_PROPS` and `CHECKSUM_SLOT_PROPS_FROM_PARENT`) name the two slots, and `calculateChecksum()`, `verifyChecksum()`, `addChecksumToData()`, and `ChildComponentPartialRenderer` thread these values through. Cross-component and cross-slot replays no longer verify.\n\nThe patch for this issue is available [here](https://github.com/symfony/ux/commit/a224b5af3e2e33ee14ac71356ae0e0877900a81c) for branch 2.x (and forward-ported to 3.x).\n\n### Credits\n\nSymfony would like to thank Anthropic (via Project Glasswing) for reporting the issue and Hugo Alliaume for providing the fix.","published":"2026-07-17T16:03:27.784Z","modified":"2026-08-12T03:51:43.651196224Z","cvss":null,"epss":{"score":0.00242,"percentile":0.15542,"asOf":"2026-09-17"},"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Packagist","name":"symfony/ux-live-component","fixedVersion":"2.36.0"},{"ecosystem":"Packagist","name":"symfony/ux-live-component","fixedVersion":"3.1.0"}],"fix":{"url":"https://github.com/symfony/ux/commit/a224b5af3e2e33ee14ac71356ae0e0877900a81c","label":"symfony/ux@a224b5a"},"references":[{"type":"WEB","url":"https://github.com/symfony/ux/releases/tag/v2.36.0"},{"type":"WEB","url":"https://github.com/symfony/ux/releases/tag/v3.1.0"},{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/49xxx/CVE-2026-49212.json"},{"type":"ADVISORY","url":"https://github.com/symfony/ux/security/advisories/GHSA-34w5-c283-j9fg"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-49212"},{"type":"FIX","url":"https://github.com/symfony/ux/commit/a224b5af3e2e33ee14ac71356ae0e0877900a81c"},{"type":"WEB","url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/ux-live-component/CVE-2026-49212.yaml"},{"type":"PACKAGE","url":"https://github.com/symfony/ux"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-12T03:51:43.651196224Z"}}