CVE-2020-8138

Severity: medium (CVSS 6.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 1.4% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2020-03-20 · updated 2026-06-17
Weakness: CWE-918

Description

A missing check for IPv4 nested inside IPv6 in Nextcloud server < 17.0.1, < 16.0.7, and < 15.0.14 allowed a Server-Side Request Forgery (SSRF) vulnerability when subscribing to a malicious calendar URL.

Affected products

Nextcloud Server: before 15.0.14; from 16.0.0 before 16.0.7; from 17.0.0 before 17.0.2 — fixed in 15.0.14, 16.0.7, 17.0.2

How to fix

Upgrade to a fixed version: Nextcloud Server 15.0.14, 16.0.7, 17.0.2. Check the vendor advisory for mitigations.

References

https://hackerone.com/reports/736867
https://nextcloud.com/security/advisory/?id=NC-SA-2020-014
https://hackerone.com/reports/736867
https://nextcloud.com/security/advisory/?id=NC-SA-2020-014

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