CVE-2021-28543
4.0 · MEDIUMOverview
CVE-2021-28543 is a medium-severity vulnerability affecting varnish-cache varnish-modules. It was published on March 16, 2021 and has a CVSS 3.1 base score of 4.0 (MEDIUM).
This vulnerability has a CVSS 3.1 base score of 4.0, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
Technical Description
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.
Remediation
Check the references section for vendor advisories and patches from varnish-cache. Update varnish-modules to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
Affected Products
| Vendor | Product | Versions | Status |
|---|---|---|---|
| varnish-cache | varnish-modules | >= 0, < 0.17.1 | Affected |
| varnish-cache | varnish-modules_klarlack | >= 0, < 0.17.1 | Affected |
References
Frequently Asked Questions
What is CVE-2021-28543?
CVE-2021-28543 is a medium-severity vulnerability affecting varnish-cache varnish-modules. It was published on March 16, 2021 and has a CVSS 3.1 base score of 4.0 (MEDIUM).
How severe is CVE-2021-28543?
This vulnerability has a CVSS 3.1 base score of 4.0, rated MEDIUM. It can be exploited remotely over the network. No authentication or special privileges are required for exploitation.
How do I fix or remediate CVE-2021-28543?
Check the references section for vendor advisories and patches from varnish-cache. Update varnish-modules to the latest patched version. If immediate patching is not possible, review the CVSS vector to understand the attack surface and apply compensating controls such as network segmentation or access restrictions.
How can CyberStrike help with CVE-2021-28543?
CyberStrike's AI-powered security agents can automatically detect CVE-2021-28543 across your infrastructure using autonomous pentesting, DAST scanning, and HackBrowser. The platform continuously monitors for known vulnerabilities and provides actionable remediation guidance prioritized by real-world exploitability.
How CyberStrike Helps
AI agents map your attack surface to find vulnerabilities like this one.
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