{"id":"UBUNTU-CVE-2026-33540","details":"Distribution is a toolkit to pack, ship, store, and deliver container content. Prior to 3.1.0, in pull-through cache mode, distribution discovers token auth endpoints by parsing WWW-Authenticate challenges returned by the configured upstream registry. The realm URL from a bearer challenge is used without validating that it matches the upstream registry host. As a result, an attacker-controlled upstream (or an attacker with MitM position to the upstream) can cause distribution to send the configured upstream credentials via basic auth to an attacker-controlled realm URL. This vulnerability is fixed in 3.1.0.","modified":"2026-07-02T18:02:30.402175471Z","published":"2026-04-06T15:17:00Z","upstream":["CVE-2026-33540"],"references":[{"type":"REPORT","url":"https://ubuntu.com/security/CVE-2026-33540"},{"type":"REPORT","url":"https://www.cve.org/CVERecord?id=CVE-2026-33540"},{"type":"REPORT","url":"https://github.com/distribution/distribution/security/advisories/GHSA-3p65-76g6-3w7r"}],"affected":[{"package":{"name":"docker-registry","ecosystem":"Ubuntu:Pro:16.04:LTS","purl":"pkg:deb/ubuntu/docker-registry?arch=source&distro=esm-apps%2Fxenial"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.1.1~ds1-4","2.1.1~ds1-4ubuntu1","2.3.0~ds1-1","2.3.0~ds1-1ubuntu0.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_version":"2.3.0~ds1-1ubuntu0.1~esm1","binary_name":"docker-registry"},{"binary_name":"golang-github-docker-distribution-dev","binary_version":"2.3.0~ds1-1ubuntu0.1~esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33540.json"}},{"package":{"name":"docker-registry","ecosystem":"Ubuntu:Pro:18.04:LTS","purl":"pkg:deb/ubuntu/docker-registry?arch=source&distro=esm-apps%2Fbionic"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.6.2~ds1-1","2.6.2~ds1-1ubuntu0.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_name":"docker-registry","binary_version":"2.6.2~ds1-1ubuntu0.1~esm1"},{"binary_version":"2.6.2~ds1-1ubuntu0.1~esm1","binary_name":"golang-github-docker-distribution-dev"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33540.json"}},{"package":{"name":"docker-registry","ecosystem":"Ubuntu:20.04:LTS","purl":"pkg:deb/ubuntu/docker-registry?arch=source&distro=focal"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.6.2~ds1-2","2.7.1~ds1-2","2.7.1~ds1-3","2.7.1~ds1-4","2.7.1+ds2-5","2.7.1+ds2-7","2.7.1+ds2-7ubuntu0.1","2.7.1+ds2-7ubuntu0.2","2.7.1+ds2-7ubuntu0.3"],"ecosystem_specific":{"binaries":[{"binary_name":"docker-registry","binary_version":"2.7.1+ds2-7ubuntu0.3"},{"binary_name":"golang-github-docker-distribution-dev","binary_version":"2.7.1+ds2-7ubuntu0.3"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33540.json"}},{"package":{"name":"docker-registry","ecosystem":"Ubuntu:Pro:22.04:LTS","purl":"pkg:deb/ubuntu/docker-registry?arch=source&distro=esm-apps%2Fjammy"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.7.1+ds2-7build2","2.8.0+ds1-4","2.8.0+ds1-4ubuntu0.1~esm1","2.8.0+ds1-4ubuntu0.1~esm2","2.8.0+ds1-4ubuntu0.1~esm3"],"ecosystem_specific":{"binaries":[{"binary_version":"2.8.0+ds1-4ubuntu0.1~esm3","binary_name":"docker-registry"},{"binary_name":"golang-github-docker-distribution-dev","binary_version":"2.8.0+ds1-4ubuntu0.1~esm3"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33540.json"}},{"package":{"name":"docker-registry","ecosystem":"Ubuntu:24.04:LTS","purl":"pkg:deb/ubuntu/docker-registry?arch=source&distro=noble"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.8.2+ds1-1build1","2.8.2+ds1-1ubuntu0.24.04.1","2.8.2+ds1-1ubuntu0.24.04.2","2.8.2+ds1-1ubuntu0.24.04.3"],"ecosystem_specific":{"binaries":[{"binary_name":"docker-registry","binary_version":"2.8.2+ds1-1ubuntu0.24.04.3"},{"binary_name":"golang-github-docker-distribution-dev","binary_version":"2.8.2+ds1-1ubuntu0.24.04.3"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33540.json"}},{"package":{"name":"docker-registry","ecosystem":"Ubuntu:25.10","purl":"pkg:deb/ubuntu/docker-registry?arch=source&distro=questing"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.8.3+ds1-2"],"ecosystem_specific":{"binaries":[{"binary_name":"docker-registry","binary_version":"2.8.3+ds1-2"},{"binary_name":"golang-github-docker-distribution-dev","binary_version":"2.8.3+ds1-2"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33540.json"}},{"package":{"name":"docker-registry","ecosystem":"Ubuntu:Pro:26.04:LTS","purl":"pkg:deb/ubuntu/docker-registry?arch=source&distro=esm-apps%2Fresolute"},"ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}],"versions":["2.8.3+ds1-2","2.8.3+ds1-2build1","2.8.3+ds1-2ubuntu0.26.04.1~esm1"],"ecosystem_specific":{"binaries":[{"binary_name":"docker-registry","binary_version":"2.8.3+ds1-2ubuntu0.26.04.1~esm1"},{"binary_name":"golang-github-docker-distribution-dev","binary_version":"2.8.3+ds1-2ubuntu0.26.04.1~esm1"}]},"database_specific":{"source":"https://github.com/canonical/ubuntu-security-notices/blob/main/osv/cve/2026/UBUNTU-CVE-2026-33540.json"}}],"schema_version":"1.7.5","severity":[{"type":"CVSS_V3","score":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"},{"type":"Ubuntu","score":"medium"}]}