Improper access control in Synapse - #VU139985
Published: July 29, 2026
Vulnerability identifier: #VU139985
CSH Severity: Low
CVSS v4.0: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N/E:U/U:Clear
CVE-ID: N/A
CWE-ID: CWE-284
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Affected software:
Synapse
Synapse
Detailed vulnerability description
The vulnerability allows a remote attacker to access unintended endpoints.
The vulnerability exists due to improper access control in some Synapse endpoints when processing URLs with extraneous trailing path data behind a reverse proxy that normalizes paths for routing. A remote attacker can send a specially crafted request to access unintended endpoints.
This issue can bypass reverse proxy rules and expose sensitive endpoints, but use of those endpoints may still require a valid access token.
Remediation
Install security update from vendor's website.