UBUNTU-CVE-2026-33540

Advisory lineage Upstream: 1 Downstream: 0
Upstream
CVE-2026-33540
Published: 06 Apr 2026, 15:17
Last modified:20 May 2026, 16:25

Vulnerability Summary

Overall Risk (default)
medium
30/100
CVSS Score
7.5 HIGH
3.1 (osv_ubuntu)
EPSS Score
No data
KEV
Not listed
Ransomware
No reports
Public exploits
None found
Dark Web
Not detected

Timeline

06 Apr 2026, 15:17
Published
Vulnerability first disclosed
20 May 2026, 16:25
Last Modified
Vulnerability information updated

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.

CVSS Metrics

  • v3.1•HIGH•Score: 7.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N

Affected Systems

  • ubuntu•docker-registry

    all | all | all | all | all

References (3)