CVE-2026-75583

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.

References

• https://github.com/ridafkih/keeper.sh
• https://github.com/ridafkih/keeper.sh/commit/aea1cf537b850509e802b388f38cf1482cb6291b
• https://github.com/ridafkih/keeper.sh/security/advisories/GHSA-mxxg-qffg-j3p6
• https://www.vulncheck.com/advisories/keeper-sh-calendar-version-prior-to-ssrf-guard-bypass-via-dns-rebinding