CKEditor 5 CVE-2026-116688

Exploitation requires the attacker to supply crafted editor content whose style attribute values reach the vulnerable es-toolkit prototype-pollution path; per the CVSS vector (PR:L) the actor needs low-level privileges, i.e. the ability to feed content into the editor rather than a fully anonymous request. The affected scope is CKEditor 5 bundling es-toolkit v1.45.1 in version ranges >=45.0.0 to <47.7.4 and >=48.0.0 to <48.5.1; versions 47.7.4 and 48.5.1 and later are not affected. This specific issue (GHSA-rh54-vffm-5fvp) is not limited to a special feature configuration per the advisory - it concerns the engine's style attribute processing. Limiting factors: the low-privilege prerequisite (PR:L), the fact that only the listed version ranges are vulnerable, and that the only complete remediation per the vendor is updating to a fixed release (which upgrades es-toolkit to v1.52.0).

This is a genuine, patch-now-grade priority within its deployment scope, though not a drop-everything emergency. The CVSS 3.1 vector (AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:N, 8.1 High) indicates a network-reachable, low-complexity flaw requiring only low privileges (PR:L) and no user interaction, with high confidentiality and integrity impact from arbitrary JavaScript execution. The vuln.today Decision label is 'this_week', consistent with a serious but not actively-exploited issue. No EPSS score was provided, so exploitation probability cannot be quantified. KEV status is absent (not listed), so there is no confirmed active exploitation - exploitation status is 'no public exploit identified at time of analysis'; the GitHub references are the vendor advisory and patch commits, not a working PoC. The signals are internally consistent: a high-CVSS XSS in a widely-embedded editor library with a vendor patch available, but no evidence of in-the-wild use. Note the PR:L qualifier matters - exploitation presumes an actor who can feed crafted content into the editor (e.g., a registered/low-privileged user), which tempers the raw network-vector reading. Real priority: yes for anyone bundling the affected CKEditor 5 ranges, but driven by exposure breadth rather than confirmed exploitation.

An attacker with the ability to submit content into a CKEditor 5 instance (for example a low-privileged authenticated user of an application embedding the editor) crafts malicious style attribute values. When the engine processes this content, the vulnerable es-toolkit version's prototype-pollution behavior is reached, resulting in unauthorized JavaScript execution in the browser. No public working exploit was identified at the time of analysis; only the vendor advisory and patch commits are available.