CVE-2026-33540
published 2026-04-06CVE-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…
PriorityP347high7.5CVSS 3.1
AVNACLPRNUINSUCHINAN
EPSS
0.27%
19.6th percentile
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
4 ranges
| Vendor | Product | Version range | Fixed in |
|---|---|---|---|
| distribution | distribution | < 3.1.0 | 3.1.0 |
| distribution_project | distribution | < 3.1.0 | 3.1.0 |
| github.com | distribution_distribution | 0 – 2.8.3 | — |
| github.com | distribution_distribution_v3 | >= 0 < 3.1.0 | 3.1.0 |
CVSS provenance
nvdv3.17.5HIGHCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N
ghsa6.1MEDIUM
osv7.5HIGH
vendor_redhat7.5HIGH
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VulDB
Distribution up to 3.0.x server-side request forgery (GHSA-3p65-76g6-3w7r / Nessus ID 305624)
vuldb·2026-04-13·CVSS 7.5
CVE-2026-33540 [HIGH] Distribution up to 3.0.x server-side request forgery (GHSA-3p65-76g6-3w7r / Nessus ID 305624)
A vulnerability has been found in Distribution up to 3.0.x and classified as critical. This affects an unknown function. This manipulation causes server-side request forgery.
This vulnerability is handled as CVE-2026-33540. The attack can be initiated remotely. There is not any exploit available.
The affected component should be upgraded.
OSV
CVE-2026-33540: Distribution is a toolkit to pack, ship, store, and deliver container content
osv·2026-04-07·CVSS 7.5
CVE-2026-33540 [HIGH] CVE-2026-33540: Distribution is a toolkit to pack, ship, store, and deliver container content
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.
OSV
Distribution affected by pull-through cache credential exfiltration via www-authenticate bearer realm
osv·2026-04-06·CVSS 6.1
CVE-2026-33540 [MEDIUM] Distribution affected by pull-through cache credential exfiltration via www-authenticate bearer realm
Distribution affected by pull-through cache credential exfiltration via www-authenticate bearer realm
hi guys,
commit: 40594bd98e6d6ed993b5c6021c93fdf96d2e5851 (as-of 2026-01-31)
contact: GitHub Security Advisory (https://github.com/distribution/distribution/security/advisories/new)
## summary
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 is the
GHSA
Distribution affected by pull-through cache credential exfiltration via www-authenticate bearer realm
ghsa·2026-04-06·CVSS 6.1
CVE-2026-33540 [MEDIUM] CWE-918 Distribution affected by pull-through cache credential exfiltration via www-authenticate bearer realm
Distribution affected by pull-through cache credential exfiltration via www-authenticate bearer realm
hi guys,
commit: 40594bd98e6d6ed993b5c6021c93fdf96d2e5851 (as-of 2026-01-31)
contact: GitHub Security Advisory (https://github.com/distribution/distribution/security/advisories/new)
## summary
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 is the
Red Hat
github.com/distribution/distribution: Distribution: Information disclosure via improper validation of authentication realm URL
vendor_redhat·2026-04-06·CVSS 7.5
CVE-2026-33540 [HIGH] CWE-918 github.com/distribution/distribution: Distribution: Information disclosure via improper validation of authentication realm URL
github.com/distribution/distribution: Distribution: Information disclosure via improper validation of authentication realm URL
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.
A flaw was found in Distribution, a toolkit for managing
No detection rules found.
No public exploits indexed.
Wiz
CVE-2026-33540 Impact, Exploitability, and Mitigation Steps | Wiz
blogs_wiz·CVSS 7.5
CVE-2026-33540 [HIGH] CVE-2026-33540 Impact, Exploitability, and Mitigation Steps | Wiz
## CVE-2026-33540 :
Wolfi vulnerability analysis and mitigation
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.
Source : NVD
## 7.5
Score
Published April 6, 2026
Severity HIGH
CNA Score 7.5
Affected Technologies
Wolfi
Ch
Bugzilla
CVE-2026-33540 github.com/distribution/distribution: Distribution: Information disclosure via improper validation of authentication realm URL
bugzilla·2026-04-06·CVSS 7.5
CVE-2026-33540 [HIGH] CVE-2026-33540 github.com/distribution/distribution: Distribution: Information disclosure via improper validation of authentication realm URL
CVE-2026-33540 github.com/distribution/distribution: Distribution: Information disclosure via improper validation of authentication realm URL
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.
2026-04-06
Published