What’s Vulnerable › Vulnerabilities

CVE-2023-23943: Blind SSRF via server URL input in the Nextcloud Mail app

• Severity: medium (CVSS 4.3 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.9% probability of exploitation in the next 30 days
• Public exploit or detection template: yes
• Published: 2023-02-06 · updated 2026-06-17
• Weakness: CWE-918

Description

Nextcloud mail is an email app for the nextcloud home server platform. In affected versions the SMTP, IMAP and Sieve host fields allowed to scan for internal services and servers reachable from within the local network of the Nextcloud Server. It is recommended that the Nextcloud Maill app is upgraded to 1.15.0 or 2.2.2. The only known workaround for this issue is to completely disable the nextcloud mail app.

Affected products

• nextcloud Mail: before 1.15.0; from 2.2.0 before 2.2.2 — fixed in 1.15.0, 2.2.2

How to fix

Upgrade to a fixed version: nextcloud Mail 1.15.0, 2.2.2. Check the vendor advisory for mitigations.

References

• https://github.com/nextcloud/mail/pull/7796
• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-8gcx-r739-9pf6
• https://hackerone.com/reports/1736390
• https://hackerone.com/reports/1741525
• https://hackerone.com/reports/1746582
• https://github.com/nextcloud/mail/pull/7796
• https://github.com/nextcloud/security-advisories/security/advisories/GHSA-8gcx-r739-9pf6
• https://hackerone.com/reports/1736390
• https://hackerone.com/reports/1741525
• https://hackerone.com/reports/1746582

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