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.).
Affected products
| Vendor | Product | Affected | Fixed |
|---|---|---|---|
| Vinyl-Cache | Vinyl Cache | < 9.0.2 | 9.0.2 |
| Varnish-Software | Varnish Cache | 9.0.0 – < 9.0.4, 6.3.0 – ≤ 8.0.2 | 9.0.4 |
Fixed in Linux distributions
Distributions backport fixes, so the version that fixes this vulnerability differs per release — upgrade to at least the version shown. From the distributions' security trackers and advisories.
Debian
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian 14 | vinyl-cache | 9.0.1-4.1 | — |
| Debian 13 | varnish | 7.7.0-3+deb13u2 | — |
| Debian 12 | varnish | No fix yet | — |
Ubuntu
Security tracker ↗| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu 26.10 | varnish +1 | No fix yet | — |
| Ubuntu 26.04 LTS | varnish | No fix yet | — |
| Ubuntu 24.04 LTS | varnish | No fix yet | — |
| Ubuntu 14.04 LTS | varnish | No fix yet | — |
Show 4 more (older releases, extended support, other products)Fewer releases
| Release | Package | Fixed in | Advisory |
|---|---|---|---|
| Ubuntu Pro 22.04 LTS | varnish | No fix yet | — |
| Ubuntu Pro 20.04 LTS | varnish | No fix yet | — |
| Ubuntu Pro 18.04 LTS | varnish | No fix yet | — |
| Ubuntu Pro 16.04 LTS | varnish | No fix yet | — |
Advisories 1
- WID-SEC-2026-3440 Varnish HTTP Cache: Schwachstelle ermöglicht Denial of Service BSI CERT-Bund (WID) · Oct 25, 2026