CVE-2026-78660 HTTP/2 Reverse Proxy - HTTP Request Smuggling

An HTTP/2 implementation in a reverse proxy forwards malformed framing-related headers to HTTP/1 clients, causing HTTP request smuggling when the HTTP/1 client is not strict, letting attackers smuggle requests.

CVSS base score 7.5 /10
High
CISA KEV
Not listed
Public exploit
None known
Authentication
Not required
EPSS
0.30% chance of exploitation in 30 days
View the NVD record ↗

Details

Type
HTTP Request Smuggling
Impact
HTTP Request Smuggling
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
Published
8 October 2026
Updated
15 October 2026
Weakness
CWE-444

Vendor fix

Update to the latest version with strict header validation and HTTP/2 to HTTP/1 proxy fixes.

Patching closes this CVE. It does not tell you which of your systems run the affected version, or what else is exposed alongside them.

References

← All CVEs