{"id":"CVE-2026-49212","title":"symfony/ux-live-component: LiveComponentHydrator HMAC checksum lacks component and slot binding","summary":"symfony/ux-live-component: LiveComponentHydrator HMAC checksum lacks component and slot binding","severity":"low","cwe":["CWE-345"],"vendor":"symfony","product":"symfony/ux-live-component","affected":["symfony/ux-live-component >= 2.8.0, < 2.36.0","symfony/ux-live-component >= 3.0.0, < 3.1.0"],"patched":["symfony/ux-live-component 2.36.0","symfony/ux-live-component 3.1.0"],"published":"2026-06-19","updated":"2026-06-19","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-34w5-c283-j9fg","references":[{"url":"https://github.com/symfony/ux/security/advisories/GHSA-34w5-c283-j9fg"},{"url":"https://github.com/symfony/ux/commit/a224b5af3e2e33ee14ac71356ae0e0877900a81c"},{"url":"https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/ux-live-component/CVE-2026-49212.yaml"},{"url":"https://github.com/advisories/GHSA-34w5-c283-j9fg"}],"tags":["ghsa","composer"],"ingestedAt":"2026-06-22T15:52:21.063Z","ecosystem":"composer","epss":0.00242,"epssPercentile":0.15627,"slug":"CVE-2026-49212","body":"## Overview\n\n### 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.\n\n## Affected packages\n\n- `symfony/ux-live-component >= 2.8.0, < 2.36.0`\n- `symfony/ux-live-component >= 3.0.0, < 3.1.0`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `symfony/ux-live-component 2.36.0`\n- `symfony/ux-live-component 3.1.0`","depth":"sunlit","depthScore":14,"depthScoreParts":{"impact":13.8,"likelihood":0,"exploitation":0,"ransomware":0},"changes":[]}