CVE-2021-28543: Null Pointer Dereference
Varnish varnish-modules before 0.17.1 allows remote attackers to cause a denial of service (daemon restart) in some configurations. This does not affect organizations that only install the Varnish Cache product; however, it is common to install both Varnish Cache and varnish-modules. Specifically, an assertion failure or NULL pointer dereference can be triggered in Varnish Cache through the varnish-modules header.append() and header.copy() functions. For some Varnish Configuration Language (VCL) files, this gives remote clients an opportunity to cause a Varnish Cache restart. A restart reduces overall availability and performance due to an increased number of cache misses, and may cause higher load on backend servers.
Affected Software
Event History
Frequently Asked Questions
What is CVE-2021-28543?
CVE-2021-28543 is a vulnerability that allows remote attackers to cause a denial of service in Varnish varnish-modules before version 0.17.1.
How does CVE-2021-28543 affect Varnish Cache and varnish-modules?
CVE-2021-28543 does not affect organizations that only install Varnish Cache, but it does affect those that install both Varnish Cache and varnish-modules.
What is the severity of CVE-2021-28543?
CVE-2021-28543 has a severity level of 7.5, which is considered high.
What is the fix for CVE-2021-28543?
To fix CVE-2021-28543, upgrade Varnish varnish-modules to version 0.17.1 or later.
Where can I find more information about CVE-2021-28543?
You can find more information about CVE-2021-28543 at the following references: [Reference 1](https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/OPFBRQUJNWHCB3GQHSSAPRLQU6Q6PY43/) and [Reference 2](https://varnish-cache.org/security/VSV00006.html).