CVE-2026-63096
MediumCVSS 5.8Exploitation Probability (EPSS)
Low risk12th percentile - higher than 12% of all known CVEs
Summary
Dendrite up to version 0.13.8 contains a server-side request forgery (SSRF) vulnerability that allows unauthenticated attackers to cause the server to open outbound TLS connections to arbitrary hosts and ports by supplying an unvalidated serverName parameter to the legacy media download endpoint. Attackers can exploit distinguishable error response classes and leaked internal IP addresses in error messages to perform blind port scanning and enumerate internal network topology.
Risk Assessment
The risk is that an attacker can perform port scanning and internal network mapping, potentially revealing sensitive services and infrastructure, and enabling further attacks on internal resources.
Recommendation
Immediately upgrade Dendrite to a version later than 0.13.8 that includes a fix for the SSRF vulnerability. Until the update is applied, restrict access to the legacy media download endpoint to trusted networks only.
Other vulnerabilities in Dendrite
See all- CVE-2026-63097Medium
Dendrite through 0.13.8 contains an improper access control vulnerability in the syncapi /context endpoint. It allows authenticated local users to access post-leave room state events by exploiting a flawed membership check.
- CVE-2026-63095Medium
Dendrite through version 0.13.8 contains an improper authorization vulnerability in the Matrix Client-Server API that allows any authenticated local user to delete third-party identifier bindings belonging to other users. Attackers can exploit the unverified Forget3PID handler to remove a victim's email or MSISDN binding and subsequently rebind the address through an identity server to hijack the victim's password reset flow.
Original NVD description (English source)
Dendrite through 0.13.8 contains a server-side request forgery vulnerability that allows unauthenticated attackers to cause the server to open outbound TLS connections to arbitrary hosts and ports by supplying an unvalidated serverName parameter to the legacy media download endpoint. Attackers can exploit distinguishable error response classes and leaked internal IP addresses in error messages to perform blind port scanning and enumerate internal network topology.