HIGH

CVE-2026-16453

Q: Is CVE-2026-16453 actively exploited?

Active exploitation of CVE-2026-16453 has not been confirmed. Its EPSS score was 0.2% on 2026-10-16, the estimated probability of exploitation in the next 30 days.

Q: What is the CVSS score for CVE-2026-16453?

CVE-2026-16453 has a CVSS v3 base score of 7.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N.

Mattermost SAML RelayState forgery allows unauthorized team membership

CVSS v3

7.1

HIGH

EPSS Score

0.2 %

exploit probability, as of 2026-10-16

CISA KEV

known exploited

Exploitation

none

SSVC status

Get an alert for each new CVE published for the software you run. Set up CVE Watch Free account · no credit card

Affected and fixed versions

Neither OSV.dev nor the vendor advisories we read list affected versions for CVE-2026-16453 yet.

Full record on NVD

Description

Mattermost versions 11.10.x <= 11.10.0, 11.7.x <= 11.7.9, 11.9.x <= 11.9.1, 11.8.x <= 11.8.5 fail to verify the integrity of the SAML RelayState POST parameter which allows an authenticated SAML user to join any team, including invite-only teams, via forging the team_id or invite_id fields in the RelayState.. Mattermost Advisory ID: MMSA-2026-00727

Technical details

CVSS v3 Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N
Published: 2026-10-16
Last Modified: 2026-10-16

Frequently asked questions

What is CVE-2026-16453?

Is CVE-2026-16453 actively exploited?

Active exploitation of CVE-2026-16453 has not been confirmed. Its EPSS score was 0.2% on 2026-10-16, the estimated probability of exploitation in the next 30 days.

What is the CVSS score for CVE-2026-16453?

CVE-2026-16453 has a CVSS v3 base score of 7.1 (HIGH severity), with vector string CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N.

Hear about the next vulnerability in your software

CVE Watch matches each new CVE to the vendors and products you list (vendor and product, not the version) and puts it in your alerts with its KEV and EPSS status.

Get alerts for this product CISA KEV additions, October 2026 Search CVEs

Already have an account? Open CVE WatchNo credit card required · 50 free checks/month · Free API key

Go further

Following what attackers exploit right now? The CISA KEV additions of the month, with their patch deadlines.
Running this software? CVE Watch alerts you to new vulnerabilities in your products.

Related vulnerabilities

Same product first, then the same vendor advisory and the same publication week.

Back to CVE Database