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.
History

Mon, 06 Apr 2026 15:30:00 +0000

Type Values Removed Values Added
Description 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.
Title Distribution affected by pull-through cache credential exfiltration via www-authenticate bearer realm
Weaknesses CWE-918
References
Metrics cvssV3_1

{'score': 7.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N'}

ssvc

{'options': {'Automatable': 'yes', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}


cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-04-06T15:04:50.154Z

Reserved: 2026-03-20T18:05:11.831Z

Link: CVE-2026-33540

cve-icon Vulnrichment

Updated: 2026-04-06T15:04:39.539Z

cve-icon NVD

Status : Received

Published: 2026-04-06T15:17:10.950

Modified: 2026-04-06T16:16:33.873

Link: CVE-2026-33540

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

No data.