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TI-2021-09619 Aliases CVE-2021-28543GHSA-jpm5-7xh4-qgjv

Varnish varnish-modules before 0.17.1 allows remote attackers to cause a denial of…

Priority LOW 36CWE-476Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
Denial of service
Confidentiality · integrity · availability
None · None · High
Fix status
No fix listed

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-476.

Summary

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.

Why it matters now

EPSS 0.01495 74th percentileScored 2026-11-07
Fix No fix listed No fixed version in the sources yet

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
——all versions—No fix listedCNA
  • — Vendor— Affected all versions Fixed in — No fix listed CNA

CPE configurations NVD · 3

CPEVersionsRoleVendor
cpe:2.3:a:varnish-cache:varnish-modules:*:*:*:*:*:*:*:*before 0.17.1VulnerableVarnish-cache
cpe:2.3:a:varnish-cache:varnish-modules_klarlack:*:*:*:*:*:*:*:*before 0.17.1VulnerableVarnish-cache
cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:*34VulnerableFedoraproject
  • cpe:2.3:a:varnish-cache:varnish-modules:*:*:*:*:*:*:*:* Versions before 0.17.1 Vulnerable ·Varnish-cache
  • cpe:2.3:a:varnish-cache:varnish-modules_klarlack:*:*:*:*:*:*:*:* Versions before 0.17.1 Vulnerable ·Varnish-cache
  • cpe:2.3:o:fedoraproject:fedora:34:*:*:*:*:*:*:* Versions 34 Vulnerable ·Fedoraproject

Remediation

No fixed version listed by the sources yet.

Vendor assessments

Red Hat

Red Hat rating: Low. Red Hat's page for this CVE →

Not affected: 3 products
  • Red Hat Enterprise Linux 8
  • Red Hat Enterprise Linux 9
  • Red Hat Software Collections

Timeline

  1. 2026-10-02 Threatist record created from CVE-2021-28543
  2. 2026-10-03 Alias added: GHSA-jpm5-7xh4-qgjv

References

Advisory 2

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences