Resource exhaustion in Microsoft Internet Information Services (IIS) - CVE-2026-49975
Published: June 4, 2026
Vulnerability identifier: #VU133362
CSH Severity: High
CVSS v4.0: 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/E:U/U:Amber
CVE-ID: CVE-2026-49975
CWE-ID: CWE-400
Exploitation vector: Remote access
Exploit availability:
No public exploit available
Vendor: Microsoft
Affected software:
Microsoft Internet Information Services (IIS)
Microsoft Internet Information Services (IIS)
Detailed vulnerability description
The vulnerability allows a remote attacker to cause a denial of service.
The vulnerability exists due to uncontrolled resource consumption in the HTTP/2 request handling and HPACK header processing when handling crafted HTTP/2 requests that use repeated indexed header references and a stalled flow-control window. A remote attacker can send specially crafted HTTP/2 requests to cause a denial of service.
The issue is reachable in the default HTTP/2 configuration.
How to mitigate CVE-2026-49975
Cybersecurity Help is currently unaware of any official solution to address this vulnerability.