Incorrect Behavior Order: Validate Before Canonicalize Affecting varnish-cache package, versions [,8.0.1)
Threat Intelligence
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
Do your applications use this vulnerable package?
In a few clicks we can analyze your entire application and see what components are vulnerable in your application, and suggest you quick fixes.
Test your applications- Snyk IDSNYK-UNMANAGED-VARNISHCACHE-15874413
- published2 Apr 2026
- disclosed27 Mar 2026
- creditTom Kinnaird
Introduced: 27 Mar 2026
CVE-2026-34475 (opens in a new tab)How to fix?
Upgrade varnish-cache to version 8.0.1 or higher.
Overview
Affected versions of this package are vulnerable to Incorrect Behavior Order: Validate Before Canonicalize in the HTTP/1.1 request if unchecked req.url gets passed to a backend which accepts requests with absolute form URIs. An attacker can manipulate cache contents or bypass authentication by crafting specific HTTP requests.
Note:
Varnish Cache LTS was patched in version 6.0.17.
Workaround
If upgrading is not possible, the problem can be mitigated by adding the following VCL snippet at the top of the VCL:
sub vsv18 { if (req.url == "*" && req.method == "OPTIONS") { return; } # NB: we do not allow connect by default (see vcl_req_method) if (req.url !~ "^/" && req.method != "CONNECT") { return (synth(400)); } }
sub vcl_recv { call vsv18; }