CVE-2026-47238: ClipBucket v5 Unauthorized Subtitle Editing Vulnerability

Technical summary

CVE-2026-47238 is an authorization bypass vulnerability (CWE-639: Authorization Bypass Through User-Controlled Key; CWE-863: Incorrect Authorization) in ClipBucket v5 prior to version 5.5.3 - #133. The subtitle management endpoints fail to validate that the requesting user owns or has permission to modify the target video's subtitles. An authenticated attacker can upload new subtitle files, rename existing ones, or delete them via direct API calls or web requests. The vulnerability requires valid authentication but no elevated privileges—a standard user account is sufficient. The network-based attack vector (CVSS AV:N), low attack complexity (AC:L), and lack of user interaction (UI:N) make this a straightforward exploit for anyone with system access.

Business impact

Unauthorized subtitle modifications can degrade user experience and platform integrity. Attackers may inject malicious or offensive captions into popular videos, damage creator reputation, or delete captions to render content inaccessible to international audiences. For platforms relying on accurate, curated subtitle libraries, this vulnerability compromises content quality assurance. The impact is localized to integrity and availability (no confidentiality breach) but affects multiple users per incident. Organizations running vulnerable ClipBucket instances should prioritize patching to restore user trust and prevent content vandalism.

Affected systems

ClipBucket v5 versions prior to 5.5.3 - #133 are vulnerable. The open-source nature means affected systems include self-hosted ClipBucket installations, community video platforms, and any derivative projects using the affected codebase. No commercial vendor product versions are implicated. Patched versions 5.5.3 - #133 and later eliminate the flaw. Administrators should verify their running version against the official release notes.

Exploitability

Exploitability is straightforward. The vulnerability requires only valid user credentials—no special privileges, complex exploitation techniques, or social engineering. An attacker can target subtitles using common web requests or API calls; no zero-click scenario exists. The network-accessible nature and lack of user interaction lower the barrier to automated or scaled attacks. However, the requirement for authenticated access prevents unauthenticated mass exploitation. Organizations with strong user account hygiene and monitoring for unusual subtitle activity can detect opportunistic abuse, though motivated adversaries may evade detection through infrequent, targeted modifications.

Remediation

Upgrade ClipBucket to version 5.5.3 - #133 or later. Verify the patched build number to ensure the authorization checks for subtitle operations are in place. For organizations unable to upgrade immediately, implement access controls at the reverse proxy or WAF level to restrict subtitle-related API endpoints, though this is a temporary measure. Review recent subtitle activity logs to identify and undo unauthorized changes. If running a custom or forked version, audit subtitle management code against the official patch to confirm equivalent fixes are applied.

Patch guidance

Download and deploy ClipBucket v5.5.3 - #133 or later from the official ClipBucket repository. Test the patch in a staging environment to confirm subtitle functionality and backward compatibility with existing captions. After deployment, verify that only the video owner (and designated admins) can upload, edit, or delete subtitles. Monitor post-patch logs for any residual unauthorized access attempts. If running a managed or hosted version, confirm with your provider that the update has been applied and tested.

Detection guidance

Monitor subtitle API endpoints for requests from users accessing subtitles they do not own. Log all subtitle modifications (upload, rename, delete) with user ID and target video ID. Establish baselines for normal subtitle activity and alert on anomalies: multiple rapid changes, bulk deletions, or modifications by low-activity accounts. Review access logs for cross-user subtitle operations pre-patch. Use video owner assertions in logs to identify mismatches between the requester and the subtitle owner. Endpoint Detection and Response (EDR) tools monitoring ClipBucket application logs can flag unauthorized subtitle operations if your logging is configured to capture user identity and target resource identifiers.

Why prioritize this

This vulnerability rates MEDIUM severity (CVSS 6.5) due to its authenticated requirement and limited scope (subtitle operations only). However, prioritize patching based on your platform's reliance on subtitle accuracy and your user base sensitivity to content integrity. If ClipBucket hosts user-generated content or serves international audiences, subtitle corruption is a reputational risk. Public-facing instances should be patched within 1–2 weeks; internal or low-traffic instances can follow within 30 days. The lack of KEV status and low exploit complexity suggest this is not currently weaponized at scale, but the ease of exploitation warrants proactive remediation.

Risk score, explained

The CVSS 6.5 score (MEDIUM) reflects: (1) network-based attack vector increasing accessibility; (2) low complexity and no special privileges needed, but (3) requirement for valid authentication limiting the attacker pool; (4) integrity and availability impact on subtitle data, but no confidentiality breach; (5) single system scope. The score does not account for business context—organizations heavily dependent on subtitle accuracy or facing regulatory requirements may assess risk higher. The absence of KEV listing and zero active exploits in the wild lower operational risk, but the vulnerability's simplicity means it could be weaponized quickly if disclosed widely.

Frequently asked questions