What’s Vulnerable › Vulnerabilities

CVE-2026-21388: Unbounded Request Body Read in MS Teams Plugin {{/lifecycle}} Webhook Endpoint

• Severity: medium (CVSS 6.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-04-09 · updated 2026-06-17
• Weakness: CWE-770

Description

Mattermost Plugins versions <=2.3.1 fail to limit the request body size on the {{/lifecycle}} webhook endpoint which allows an authenticated attacker to cause memory exhaustion and denial of service via sending an oversized JSON payload. Mattermost Advisory ID: MMSA-2026-00610

Affected products

• Mattermost: through 2.3.1

References

• https://mattermost.com/security-updates

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