Vulnerability Details CVE-2026-33540
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.
Exploit prediction scoring system (EPSS) score
EPSS Score 0.0
EPSS Ranking 7.6%
CVSS Severity
CVSS v3 Score 7.5
References
Products affected by CVE-2026-33540
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cpe:2.3:a:distribution_project:distribution:*