Vulnerability · Published Apr 6, 2026 · Assigned by GitHub_M
CVE-2026-33540Distribution affected by pull-through cache credential exfiltration via www-authenticate bearer realm
High 7.5
In plain English
A high-severity server-side request forgery in distribution from distribution. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.3% (higher than 21% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official 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.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:12 | docker-registry | no fix listed | DEBIAN-CVE-2026-33540 |
| Debian:13 | docker-registry | no fix listed | DEBIAN-CVE-2026-33540 |
| Debian:14 | docker-registry | 2.8.3+ds1-3 | DEBIAN-CVE-2026-33540 |
| Go | github.com/distribution/distribution | no fix listed | GO-2026-5094 |
| Go | github.com/distribution/distribution | no fix listed | GHSA-3p65-76g6-3w7r |
| Go | github.com/distribution/distribution/v3 | 3.1.0 | GHSA-3p65-76g6-3w7r |
| Go | github.com/distribution/distribution/v3 | 3.1.0 | GO-2026-5094 |
| Ubuntu:24.04:LTS | docker-registry | no fix listed | UBUNTU-CVE-2026-33540 |
| Ubuntu:25.10 | docker-registry | no fix listed | UBUNTU-CVE-2026-33540 |
| Ubuntu:26.10 | docker-registry | no fix listed | UBUNTU-CVE-2026-33540 |
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| distribution | distribution | < 3.1.0 |
Weakness: CWE-918 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N