---
id: "CVE-2026-3303"
kind: "vulnerability"
aliases: ["CVE-2026-3303"]
title: "IBM Concert: permissive CORS lets outside sites act as users"
severity: "low"
cvss: 3.7
epss: null
exploited: false
status: "open"
category: "vendor"
products: []
ecosystems: []
tags: ["ibm-concert", "self-hosted", "vendor"]
not_affected_if: ["not-ibm-concert", "patched-version"]
published_at: "2026-10-19T18:17:07+00:00"
first_seen_at: "2026-10-23T21:57:18+00:00"
updated_at: "2026-10-25T04:44:04+00:00"
sources: [{"source": "nvd", "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-3303", "first_seen_at": "2026-10-23T21:57:18+00:00"}]
---

# IBM Concert: permissive CORS lets outside sites act as users

IBM Concert versions 1.0 through 3.0.0 accept cross-origin requests from domains that are not on a trusted list. A malicious web page could make a logged-in user's browser perform privileged actions in Concert.

_Summary, check and fix written by a model from the sources; labelled as such._

## How to check

- Confirm whether your team runs IBM Concert and which version is deployed, using the product's about or version page.
- unknown

## Fix

- Move IBM Concert to a release later than `3.0.0`, as listed in the IBM advisory.
- unknown

## Timeline

- 2026-10-23T21:57:18+00:00 nvd https://nvd.nist.gov/vuln/detail/CVE-2026-3303

## From the sources

IBM Concert 1.0 through 3.0.0 uses cross-origin resource sharing (CORS) which could allow an attacker to carry out privileged actions as the domain name is not being limited to only trusted domains.

---

_Free to read at a human pace. An API with keys and an MCP server are in preparation; early access: hello@infrastack.ai_