Always-Incorrect Control Flow Implementation Affecting varnish-cache package, versions [,9.0.1)
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.
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Test your applications- Snyk IDSNYK-UNMANAGED-VARNISHCACHE-16109722
- published19 Apr 2026
- disclosed12 Apr 2026
- creditUnknown
Introduced: 12 Apr 2026
CVE-2026-40394 (opens in a new tab)How to fix?
Upgrade varnish-cache to version 9.0.1 or higher.
Overview
Affected versions of this package are vulnerable to Always-Incorrect Control Flow Implementation in the process that handles HTTP/2 session upgrades from HTTP/1. An attacker can cause the service to crash by sending crafted requests that manipulate the amount of prefetched data during the upgrade, leading to exhaustion of allocated workspace and a daemon panic.