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Description

Mattermost versions 10.11.x <= 10.11.12, 11.5.x <= 11.5.0, 11.4.x <= 11.4.2, 11.3.x <= 11.3.2 fail to enforce atomic single-use consumption of guest magic link tokens, which allows an attacker with access to a valid magic link to establish multiple independent authenticated sessions via concurrent requests.. Mattermost Advisory ID: MMSA-2026-00624

PUBLISHED Reserved 2026-03-05 | Published 2026-04-15 | Updated 2026-04-15 | Assigner Mattermost




MEDIUM: 6.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N

Problem types

CWE-367: Time-of-check Time-of-use (TOCTOU) Race Condition

Product status

Default status
unaffected

10.11.0 (semver)
affected

11.5.0 (semver)
affected

11.4.0 (semver)
affected

11.3.0 (semver)
affected

11.6.0
unaffected

10.11.13
unaffected

11.5.1
unaffected

11.4.3
unaffected

11.3.3
unaffected

Credits

Edgar Bellot Micó finder

References

mattermost.com/security-updates (MMSA-2026-00624) vendor-advisory

cve.org (CVE-2026-3590)

nvd.nist.gov (CVE-2026-3590)

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