CVE-2026-33540 | Distribution affected by pull-through cache credential exfiltration via www-authenticate bearer realm

Exp

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.

Published: 2026-04-06 Last update: 2026-04-09 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-33540 is rated Exploit Available (51/100): CVSS High severity, with low exploitation likelihood (EPSS 0.06%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2026-33540

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-33540

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-18 0.03% 0.06% +0.03%
2 2026-04-07 — 0.03% —

Full EPSS history (2 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-33540

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:N/A:N Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:H)
Serious risk that confidential data gets exposed in a big way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:N)
Service keeps running; no real outage angle.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2026-33540

GitHub Security Advisory for CVE-2026-33540

GHSA-3p65-76g6-3w7r · Severity: high · Ecosystem: go — Distribution affected by pull-through cache credential exfiltration via www-authenticate bearer realm

OS Trackers for CVE-2026-33540

vendor priority summary link
debian not yet assigned CVE-2026-33540 not yet assigned priority: Debian including 1 source packages (docker-registry), 5 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): open 5. https://security-tracker.debian.org/tracker/CVE-2026-33540
redhat medium — https://access.redhat.com/security/cve/CVE-2026-33540
suse medium — https://www.suse.com/security/cve/CVE-2026-33540/
ubuntu medium CVE-2026-33540 medium priority: Ubuntu including 1 source packages (docker-registry), 7 status rows across 7 suites (bionic, focal, jammy, noble, questing, upstream, xenial): needs-triage 7. https://ubuntu.com/security/CVE-2026-33540

Affected software / configurations for CVE-2026-33540

Vendor Product Version Raw CPE
distribution_project distribution < 3.1.0 cpe:2.3:a:distribution_project:distribution:*:*:*:*:*:go:*:*

References for CVE-2026-33540

cvelogic Threat Intelligence