CVE-2026-82280: Quivr Authentication Bypass Vulnerability

CVE-2026-82280 Overview

CVE-2026-82280 is a broken access control vulnerability in Quivr through version 0.0.322. The application fails to validate ownership in prompt endpoints, allowing any authenticated user to modify prompts by identifier. Attackers with read-only access to a shared brain can enumerate exposed prompt identifiers and overwrite system prompts. The overwritten prompts then affect every user of the affected brain. The flaw is classified under CWE-639: Authorization Bypass Through User-Controlled Key.

Critical Impact

An authenticated attacker with minimal privileges can alter system prompts across shared Quivr brains, manipulating AI responses for all users of the affected brain.

Affected Products

• Quivr versions through 0.0.322
• Quivr backend prompt module (backend/api/quivr_api/modules/prompt/controller/prompt_routes.py)
• Deployments exposing shared brains to multiple authenticated users

Discovery Timeline

• 2026-08-28 - CVE-2026-82280 published to NVD
• 2026-08-31 - Last updated in NVD database

Technical Details for CVE-2026-82280

Vulnerability Analysis

Quivr is an open-source generative AI knowledge assistant that organizes content into brains, each configured with prompts that guide model behavior. The prompt routes in prompt_routes.py accept requests that reference prompts by identifier but do not verify that the requesting user owns the target prompt. Any authenticated user can therefore invoke prompt modification endpoints against prompts belonging to other users or shared brains.

Because system prompts steer the behavior of the underlying language model, an attacker can inject instructions that leak brain contents, redirect users to malicious content, or degrade model output. The impact scales with the number of users consuming the affected brain.

Root Cause

The root cause is missing ownership validation on prompt endpoints. The controller trusts the prompt identifier supplied by the client and executes the update without confirming that the authenticated user created the prompt or has administrative rights over the associated brain. This is a textbook Insecure Direct Object Reference pattern tracked as CWE-639.

Attack Vector

An attacker authenticates to a Quivr instance with a low-privilege account, such as read-only membership in a shared brain. The attacker retrieves prompt identifiers that are exposed through brain metadata or API responses. Using the update endpoint defined in the Quivr prompt controller, the attacker submits a PUT request referencing a prompt they do not own and supplies attacker-controlled content. The server processes the request without an authorization check, and the modified system prompt is served to all subsequent brain users. Technical details are documented in the VulnCheck Advisory on Quivr and GitHub Issue #3698.

No verified public exploit code is available. See the Quivr API Prompt Routes Code for the vulnerable controller.

Detection Methods for CVE-2026-82280

Indicators of Compromise

• Unexpected changes to prompt content or updated_at timestamps in the Quivr prompt table that do not match the prompt owner's identity.
• API access logs showing PUT or PATCH requests to /prompts/{prompt_id} from users who did not create the referenced prompt.
• Anomalous brain behavior reported by end users, such as off-topic responses or instructions to visit external URLs.

Detection Strategies

• Correlate prompt mutation events against brain and prompt ownership records to identify cross-user modifications.
• Baseline the frequency of prompt update calls per user and alert on outliers, particularly from read-only members of shared brains.
• Review web server and reverse proxy logs for enumeration patterns targeting prompt identifiers.

Monitoring Recommendations

• Forward Quivr backend and API gateway logs to a central analytics platform and retain them for post-incident review.
• Monitor the Quivr database for direct writes to the prompt table outside expected application flows.
• Track authentication events for accounts that suddenly perform administrative-style API calls.

How to Mitigate CVE-2026-82280

Immediate Actions Required

• Restrict Quivr access to trusted users and revoke unnecessary memberships on shared brains until a patched release is deployed.
• Audit existing prompts in every shared brain and restore known-good content from version control or backups.
• Rotate API tokens and session credentials for users who had access to shared brains during the exposure window.

Patch Information

At the time of publication, no fixed release is referenced in the NVD entry. Monitor the GitHub Quivr Repository and GitHub Issue #3698 for a patched version that adds ownership validation to the prompt controller. When a fix is released, upgrade beyond 0.0.322 and confirm that the prompt update handler enforces an ownership or brain-role check before persisting changes.

Workarounds

• Apply a reverse proxy rule that blocks non-owner PUT and PATCH requests to /prompts/{prompt_id} based on the authenticated principal.
• Limit shared brain membership to trusted users and avoid granting read access to untrusted collaborators until the fix is applied.
• Add a local patch to prompt_routes.py that resolves the prompt owner and rejects requests when the authenticated user identifier does not match.

# Configuration example: block prompt modification at the reverse proxy layer
# Example NGINX snippet - adjust to your deployment before use
location ~ ^/prompts/[^/]+$ {
    limit_except GET {
        deny all;
    }
    proxy_pass http://quivr_backend;
}