Quick answers
- Is CVE-2026-19541 exploited in the wild?
- No. Junglewise Threat Intelligence has no report of CVE-2026-19541 being exploited in the wild.
- How severe is CVE-2026-19541?
- Medium severity, with a CVSS score of 6.5, published 16 October 2026.
- Which products and versions are affected?
- Mattermost Server 11.7 through 11.7.10, 11.8 through 11.8.5, 11.9 through 11.9.1, 11.10 through 11.10.1.
- Is there a fix for CVE-2026-19541?
- Yes: fixed in Mattermost Server 11.7.11, 11.8.6, 11.9.2, 11.10.2. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
- How is CVE-2026-19541 attacked?
- It is attacked over the network, in a hosted service.
- Am I affected by CVE-2026-19541?
- Check whether you run Mattermost Server at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.
How to fix
- Fixed in: Mattermost Server 11.7.11, 11.8.6, 11.9.2, 11.10.2
Technical details
The vulnerability is an information disclosure issue in outgoing OAuth connection validation that fails to re-authenticate or re-validate the client secret before sending it to the token URL during validation. An authenticated administrator can exploit this by modifying the token URL to point to an attacker-controlled endpoint, causing the client secret to be transmitted in plaintext. No user interaction beyond the initial validation trigger is required.
Affected products
- Mattermost Mattermost Server 11.7 through 11.7.10, 11.8 through 11.8.5, 11.9 through 11.9.1, 11.10 through 11.10.1
Timeline
- 2026-10-16: disclosed