Input validation error in Synapse - #VU139987
Published: July 29, 2026
Vulnerability identifier: #VU139987
CSH Severity: Medium
CVSS v4: 8.7 [CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N]
CVE-ID: N/A
CWE-ID: CWE-20
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vulnerability details
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to improper input validation in multipart/form-data request handling when processing malicious multipart/form-data requests with a varied-case Content-Type header. A remote attacker can send a specially crafted request to cause a denial of service.
The issue can exhaust all available memory, causing the service to become unresponsive or be terminated.
Affected software
Synapse
Remediation
Install security update from vendor's website.
Synapse - update to 1.157.2