{"id":"CVE-2026-33540","summary":"Distribution affected by pull-through cache credential exfiltration via www-authenticate bearer realm","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.","aliases":["GHSA-3p65-76g6-3w7r"],"modified":"2026-04-12T04:30:21.966623Z","published":"2026-04-06T14:55:04.812Z","related":["CGA-4fxm-pmfg-6hjw"],"database_specific":{"osv_generated_from":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33540.json","cwe_ids":["CWE-918"],"cna_assigner":"GitHub_M"},"references":[{"type":"ADVISORY","url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/33xxx/CVE-2026-33540.json"},{"type":"ADVISORY","url":"https://github.com/distribution/distribution/security/advisories/GHSA-3p65-76g6-3w7r"},{"type":"ADVISORY","url":"https://nvd.nist.gov/vuln/detail/CVE-2026-33540"}],"affected":[{"ranges":[{"type":"GIT","repo":"https://github.com/distribution/distribution","events":[{"introduced":"0"},{"fixed":"708f8d6b060248fe7192294dd5440320ffc86da0"}],"database_specific":{"source":"AFFECTED_FIELD","extracted_events":[{"introduced":"0"},{"fixed":"3.1.0"}]}}],"versions":["docs-v2.4.1-2016-06-28","v2.0.0","v2.0.0-alpha.0","v2.0.0-alpha.1","v2.0.0-alpha.2","v2.0.0-alpha.3","v2.0.0-rc.0","v2.0.0-rc.1","v2.0.0-rc.2","v2.0.0-rc.3","v2.0.0-rc.4","v2.1.0","v2.1.0-rc.0","v2.1.1","v2.2.0","v2.2.1","v2.3.0-alpha","v2.3.0-rc.0","v2.3.0-rc.1","v2.3.0-rc.2","v2.4.0-rc.1","v2.5.0-rc.1","v2.6.0-rc.1","v2.7.0","v2.7.0-rc.0","v3.0.0","v3.0.0-alpha.1","v3.0.0-beta.1","v3.0.0-rc.1","v3.0.0-rc.2","v3.0.0-rc.3","v3.0.0-rc.4"],"database_specific":{"source":"https://storage.googleapis.com/osv-test-cve-osv-conversion/osv-output/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"}]}