CVE-2026-93894 Memory corruption in Varnish Cache
A buffer overflow in VCL string methods allows remote attackers to cause a denial of service by crashing the child process.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-93894?
CVE-2026-93894 is a low-severity memory corruption vulnerability in Varnish-Software Varnish Cache, published on 18 Sep 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
In Vinyl Cache before 9.0,2, workspace buffer overflow vulnerability was found in the .upper() and .lower() string type methods of VCL. This can be used as a remote denial of service (DoS) vector to make the child process segfault or assert, and then restart. Effectively exploiting this vulnerability requires prior knowledge about the VCL in use and the ability to craft a request that contains a string that is long enough to fill the remaining workspace at the call site while staying under the different request size limits (http_req_size, http_req_hdr_len, etc.).
Weakness: CWE-787
Which versions are affected by CVE-2026-93894?
How do I fix CVE-2026-93894?
Upgrade to a fixed version.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-93894 being exploited?
There is no known exploitation of CVE-2026-93894 in the wild and no public exploit code.
Sources
Also known as DEBIAN-CVE-2026-93894, GHSA-pfj3-384h-g8q8, UBUNTU-CVE-2026-93894.