{"id":"CVE-2026-50279","title":"Craft CMS: Authorship spoofing in `entries/save-entry` via pre-check/post-mutation authorization gap","summary":"Craft CMS: Authorship spoofing in `entries/save-entry` via pre-check/post-mutation authorization gap","severity":"high","cwe":["CWE-285"],"vendor":"craftcms","product":"craftcms/cms","ecosystem":"composer","affected":["craftcms/cms >= 5.0.0-RC1, < 5.9.21"],"patched":["craftcms/cms 5.9.21"],"published":"2026-07-02","updated":"2026-07-02","source":"GHSA","sourceUrl":"https://github.com/advisories/GHSA-qq2c-2q8j-jh27","references":[{"url":"https://github.com/craftcms/cms/security/advisories/GHSA-qq2c-2q8j-jh27"},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-50279"},{"url":"https://github.com/craftcms/cms/commit/9cc493be8b414d7116c7f2bc2a6d0926e73f1248"},{"url":"https://github.com/advisories/GHSA-qq2c-2q8j-jh27"}],"tags":["ghsa","composer"],"epss":0.00364,"epssPercentile":0.30155,"ingestedAt":"2026-07-02T19:41:50.970Z","slug":"CVE-2026-50279","body":"## Overview\n\n### Summary\n\n`EntriesController::actionSaveEntry()` performs entry-edit permission checks before request-controlled author changes are applied to the model. The subsequent author mutation path accepts attacker-supplied `authors` / `author` parameters and allows the change when the current user is one of the old authors. Because the controller does not re-run authorization after mutating the author list, a low-privileged user can reassign an entry’s authorship to another user without holding the dedicated peer-author-change permission.\n\n### Details\nThe control flow begins in [EntriesController.php](/D:/files/projects/cms-5.9.19/cms-5.9.19/src/controllers/EntriesController.php):249. `actionSaveEntry()` loads the entry and enforces edit permissions before calling `_populateEntryModel()`:\n\n```php\npublic function actionSaveEntry(bool $duplicate = false): ?Response\n{\n    ...\n    $entry = $this->_editableEntry($this->request->getBodyParam('entryId'), $siteId);\n    ...\n    $this->enforceEditEntryPermissions($entry, $duplicate);\n    ...\n    $this->_populateEntryModel($entry);\n    ...\n    $success = Craft::$app->getElements()->saveElement($entry);\n}\n```\n\nThe attacker-controlled source is in [EntriesController.php](/D:/files/projects/cms-5.9.19/cms-5.9.19/src/controllers/EntriesController.php):588:\n\n```php\n$entry->setAttributesFromRequest(array_filter([\n    'authorIds' => $this->request->getBodyParam('authors') ??\n        $this->request->getBodyParam('author') ??\n        $entry->getAuthorId() ??\n        static::currentUser()->id,\n]));\n```\n\n`Entry::setAttributesFromRequest()` in [Entry.php](/D:/files/projects/cms-5.9.19/cms-5.9.19/src/elements/Entry.php):1124 extracts the new author IDs and applies them if `canChangeAuthor()` returns true:\n\n```php\nif (\n    ($authorIds !== null || $authorId !== null) &&\n    $this->canChangeAuthor()\n) {\n    $this->_oldAuthorIds = $oldAuthorIds;\n    $this->setAuthorIds($authorIds);\n}\n```\n\n`canChangeAuthor()` at [Entry.php](/D:/files/projects/cms-5.9.19/cms-5.9.19/src/elements/Entry.php):2789 allows the author change when the current user can view peer entries and is already one of the existing authors:\n\n```php\nreturn (\n    empty($authorIds) ||\n    in_array($user->id, $authorIds) ||\n    $user->can(\"changeAuthorForPeerEntries:$section->uid\")\n);\n```\n\nAfter the author list is mutated, the controller does not re-check authorization. \n\nThis closes the exploit chain:\n\n1. External source: authenticated request to `entries/save-entry` with attacker-controlled `authors[]`.\n2. Trust boundary failure: authorization is checked on the pre-mutation entry state, not on the post-mutation author assignment.\n3. Privileged sink: the author relationship is rewritten in persistent storage.\n\nPreconditions derived from the source:\n\n1. The attacker is authenticated and can edit entry `345`.\n2. The attacker is among the existing authors of entry `345`, or otherwise satisfies `canChangeAuthor()` through the old author set.\n3. The attacker has `viewPeerEntries` for the section.\n4. User ID `1` exists and can be assigned as an author in that section.\n\nResult:\n\n1. `enforceEditEntryPermissions()` succeeds on the original entry state.\n2. `_populateEntryModel()` reads `authors[]=1` from the request body.\n3. `setAttributesFromRequest()` updates `authorIds` because `canChangeAuthor()` is evaluated against the old authorship state.\n4. `saveElement()` persists the change and `_saveAuthors()` rewrites the entry-author relation.\n5. Entry `345` now appears authored by user `1`.\n\n### Impact\n\nThis allows low-privileged users to falsify content ownership and alter the authorship of entries without having the dedicated author-management permission. The impact includes corrupted audit trails, misleading notifications, broken approval workflows, and unauthorized reassignment of content responsibility.\n\n## Affected packages\n\n- `craftcms/cms >= 5.0.0-RC1, < 5.9.21`\n\n## Remediation\n\nUpgrade to a patched release:\n\n- `craftcms/cms 5.9.21`","depth":"twilight","depthScore":41,"depthScoreParts":{"impact":41.3,"likelihood":0.1,"exploitation":0,"ransomware":0},"changes":[]}