Impact

A request forgery attack can be performed on Varnish Cache servers that have the HTTP/2 protocol turned on. An attacker may introduce characters through the HTTP/2 pseudo-headers that are invalid in the context of an HTTP/1 request line, causing the Varnish server to produce invalid HTTP/1 requests to the backend. This may in turn be used to successfully exploit vulnerabilities in a server behind the Varnish server.
-- https://varnish-cache.org/security/VSV00011.html#vsv00011

Patches

This is fixed in Varnish 6.0.11; Varnish 6.0.11 is available in kube-httpcache versions v0.7.1 and later.

Workarounds

See upstream mitigation hints.

References

• https://varnish-cache.org/security/VSV00011.html#vsv00011