CVE-2026-81897
CVE-2026-81897 is a Cross-site Scripting (XSS) vulnerability. O3 Security confirms whether CVE-2026-81897 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
In Concrete CMS below CMS 9.5.3, the save_control action in the Express entities forms dashboard controller did not validate the anti-CSRF token. By causing an authenticated administrator…
Description
In Concrete CMS below CMS 9.5.3, the save_control action in the Express entities forms dashboard controller did not validate the anti-CSRF token. By causing an authenticated administrator to submit a forged cross-site request, a remote attacker without credentials could write attacker-controlled headline and body values to an existing Express form Text control. Those values were emitted without output encoding by the Express form Text element, so the injected markup executed as persistent JavaScript for any administrator who later opened the affected entry, resulting in stored cross-site scripting. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.7 with vector CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Yonatan Drori from Tenzai for reporting.
Detection & mitigation playbook
VulnerabilityDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for the affected component. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Remediation status
No patched version of the affected component has shipped for CVE-2026-81897 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Mitigate without a patch
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-81897 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-81897. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-81897 in your dependencies?
O3 detects CVE-2026-81897 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.