CVE-2026-75583: keeper.sh Calendar version prior to 2.18.14 SSRF Guard Bypass via DNS Rebinding

Severity: low (CVSS 3.5 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: 2026-08-19 · updated 2026-09-24
Weakness: CWE-918

Description

keeper.sh's calendar module version prior to 2.18.14 contains a server-side request forgery (SSRF) guard bypass vulnerability that allows authenticated attackers to reach private network addresses by exploiting a DNS rebinding attack against the two-phase URL validation and connection flow. The SSRF guard validates a hostname's resolved IP addresses but discards them before the actual HTTP connection is opened, allowing an attacker who controls authoritative DNS to return a public address during validation and a private address during the subsequent independent socket-level DNS resolution, causing the guard to pass while the outbound connection reaches internal infrastructure such as cloud instance metadata endpoints.

Affected products

ridafkih keeper.sh: before 2.18.14 — fixed in 2.18.14

How to fix

Upgrade to a fixed version: ridafkih keeper.sh 2.18.14. Check the vendor advisory for mitigations.

References

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