{"id":"CVE-2026-33540","aliases":["GHSA-3p65-76g6-3w7r","GO-2026-5094"],"url":"https://o3.security/vulnerability/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.","published":"2026-04-06T14:55:04.812Z","modified":"2026-08-07T11:50:53.910908812Z","cvss":{"score":7.5,"severity":"HIGH","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N"},"epss":null,"cisaKev":null,"exploitsKnown":0,"affectedPackages":[{"ecosystem":"Go","name":"github.com/distribution/distribution/v3","fixedVersion":"3.1.0"},{"ecosystem":"Go","name":"github.com/distribution/distribution","fixedVersion":null}],"fix":null,"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"}],"provenance":{"sources":["OSV.dev","FIRST.org (EPSS)"],"lastVerified":"2026-08-07T11:50:53.910908812Z"}}