CVE-2026-81903
CVE-2026-81903 is a Cross-site Scripting (XSS) vulnerability. O3 Security confirms whether CVE-2026-81903 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Concrete CMS versions 9.0.0 to 9.5.2 stored the Page Container icon value submitted through the dashboard without validating it against the set of known container icons. The unvalidated…
Description
Concrete CMS versions 9.0.0 to 9.5.2 stored the Page Container icon value submitted through the dashboard without validating it against the set of known container icons. The unvalidated value was later concatenated into the src attribute of an img tag by a helper that did not encode attribute output, and was rendered raw in the Containers dashboard list and editor views. A user with delegated access to the Page Containers dashboard could store a crafted icon value that broke out of the src attribute and executed script in the authenticated session of another editor or administrator who viewed the list, enabling session token theft and privileged dashboard actions. The Concrete CMS security team gave this vulnerability a CVSS v4.0 score of 7.0 with vector CVSS:4.0/AV:A/AC:L/AT:N/PR:H/UI:P/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N. Thanks Andrew Gonzalez 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-2026-81903 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-2026-81903 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-2026-81903. 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-2026-81903 in your dependencies?
O3 detects CVE-2026-81903 across dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.