{"id":"CVE-2021-28543","aliases":["EUVD-2021-15219","GHSA-jpm5-7xh4-qgjv"],"status":"published","title":"Varnish varnish-modules before 0.17.1 allows remote attackers to cause a denial of service ...","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.","severity":{"version":"3.1","score":4,"vector":"CVSS:3.1/AC:H/AV:N/A:L/C:N/I:N/PR:N/S:C/UI:N","level":"medium","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.01495,"percentile":0.74523,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-476","CWE-617"],"published":"2021-03-16T14:43:04Z","modified":"2026-06-17T03:46:30Z","products":[{"vendor":"fedoraproject","product":"fedora"},{"vendor":"varnish-cache","product":"varnish-modules"},{"vendor":"varnish-cache","product":"varnish-modules_klarlack"}],"references":[{"url":"https://varnish-cache.org/security/VSV00006.html","tags":["x_refsource_MISC","x_transferred","Vendor Advisory"]},{"url":"https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/OPFBRQUJNWHCB3GQHSSAPRLQU6Q6PY43/","tags":["vendor-advisory","x_refsource_FEDORA","x_transferred"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2021-28543"},{"url":"https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/OPFBRQUJNWHCB3GQHSSAPRLQU6Q6PY43/"},{"url":"https://github.com/advisories/GHSA-jpm5-7xh4-qgjv"}],"sources":{"cve":[{"id":"CVE-2021-28543","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.","status":"published","published":"2021-03-16T14:43:04Z","modified":"2024-08-03T21:47:32.984Z","cvss":[{"version":"3.1","score":4,"vector":"CVSS:3.1/AC:H/AV:N/A:L/C:N/I:N/PR:N/S:C/UI:N","level":"medium","assessor":"cna"}],"updated_at":"2026-11-02T14:33:09.175141Z"}],"euvd":[{"id":"EUVD-2021-15219","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.","status":"published","published":"2021-03-16T14:43:04Z","modified":"2024-08-03T21:47:32Z","cvss":[{"version":"3.1","score":4,"vector":"CVSS:3.1/AC:H/AV:N/A:L/C:N/I:N/PR:N/S:C/UI:N","level":"medium"}],"updated_at":"2026-11-03T03:24:46.751124Z"}],"ghsa":[{"id":"GHSA-jpm5-7xh4-qgjv","title":"Varnish varnish-modules before 0.17.1 allows remote attackers to cause a denial of service ...","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.","status":"published","published":"2022-05-24T22:01:29Z","modified":"2023-01-27T05:03:36Z","cvss":[{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high"}],"cwes":["CWE-476"],"updated_at":"2026-11-02T14:42:16.640621Z"}],"nvd":[{"id":"CVE-2021-28543","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.","status":"published","published":"2021-03-16T15:15:13.843Z","modified":"2026-06-17T03:46:30.047Z","cvss":[{"version":"3.1","score":4,"vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:N/I:N/A:L","level":"medium","assessor":"secondary"},{"version":"3.1","score":7.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","level":"high","assessor":"primary"},{"version":"2.0","score":5,"vector":"AV:N/AC:L/Au:N/C:N/I:N/A:P","level":"medium","assessor":"primary"}],"cwes":["CWE-476","CWE-617"],"updated_at":"2026-11-02T14:06:50.805771Z"}]}}