Microsoft rejects crucial Azure vulnerability report, no CVE issued

A security researcher claims Microsoft quietly fastened an Azure Backup for AKS vulnerability after rejecting his report, and blocking a CVE from being issued.

The researcher’s report describes a crucial privilege escalation flaw that allowed cluster-admin entry from the low-privileged “Backup Contributor” position.

Microsoft disputes the declare, telling BleepingComputer the conduct was anticipated and that “no product adjustments have been made,” regardless of the researcher documenting new permission checks and failed exploit makes an attempt after disclosure, suggestive of a silent patch.

CERT agrees it is a bug, however Microsoft blocks CVE

Safety researcher Justin O’Leary found the security flaw this March, and reported it to Microsoft on March 17.

Microsoft Safety Response Middle (MSRC) rejected the report on April 13, claiming the difficulty solely concerned acquiring cluster-admin on a cluster the place “the attacker already held administrator entry,” a characterization O’Leary says misrepresents the assault totally.

“That is factually incorrect,” states the researcher.

“The vulnerability permits a consumer with zero Kubernetes permissions to achieve cluster-admin. The assault doesn’t require present cluster entry — it grants it.”

O’Leary additional says that Microsoft described the submission to MITRE as “AI-generated content material,” one thing he says didn’t tackle the technical deserves of the report.

After the rejection, O’Leary escalated the difficulty to CERT Coordination Middle, which independently validated the vulnerability on April 16 and, based on the researcher, assigned it an identifier, VU#284781:

CERT/CC had initially scheduled public disclosure for June 1, 2026, however that disclosure by no means occurred.

On Could 4, Microsoft workers reportedly contacted MITRE recommending towards CVE project, once more arguing the difficulty required pre-existing administrative entry:

CERT/CC later closed the case underneath CNA hierarchy guidelines, successfully leaving Microsoft (which is a CNA) with remaining authority over CVE issuance for its personal merchandise.

How the assault labored

Azure Backup for AKS makes use of Trusted Entry to grant backup extensions cluster-admin privileges inside Kubernetes clusters.

In line with O’Leary, the flaw allowed anybody with solely the Backup Contributor position on a backup vault to set off that Trusted Entry relationship with out already having Kubernetes permissions.

An attacker might allow backup on a goal AKS cluster, inflicting Azure to robotically configure Trusted Entry with cluster-admin privileges. From there, an attacker might extract secrets and techniques by backup operations or restore malicious workloads into the cluster.

O’Leary labeled the difficulty as a Confused Deputy vulnerability (CWE-441), the place Azure RBAC and Kubernetes RBAC belief boundaries interacted in a way that bypassed anticipated authorization controls.

Microsoft says no adjustments made, conduct says in any other case

BleepingComputer reached out to Microsoft to grasp if the tech large thought of this discovering to be a sound security vulnerability.

A Microsoft spokesperson informed BleepingComputer:

“Our evaluation concluded that this isn’t a security vulnerability, however slightly anticipated conduct that requires pre-existing administrative privileges throughout the buyer’s atmosphere. Due to this fact, no product adjustments have been made to handle this report and no CVE or CVSS rating have been issued.”

Nonetheless, following the disclosure of his report this month, O’Leary noticed that the unique assault path now not works.

“Present conduct returns errors that didn’t exist in March 2026,” he states:

ERROR: UserErrorTrustedAccessGatewayReturnedForbidden
“The Trusted Entry position binding is lacking/has gotten eliminated”

In line with O’Leary, Azure Backup for AKS now requires Trusted Entry to be manually configured earlier than backup may be enabled, reversing the sooner conduct the place Azure configured it robotically.

He additionally noticed further permission checks that have been absent throughout his authentic testing in March. The vault MSI now requires Reader permissions on each the AKS cluster and snapshot useful resource group, whereas the AKS cluster MSI requires Contributor permissions on the snapshot useful resource group.

In different phrases, the vulnerability seems to have been fastened, however Microsoft has neither issued a public advisory nor notified clients.

The visibility downside for defenders

With no CVE or advisory, defenders have little visibility into the publicity window or remediation timeline.

“Organizations that granted Backup Contributor between an unknown begin date and Could 2026 have been uncovered to privilege escalation,” writes the researcher.

“With no CVE, security groups can’t monitor this publicity. Silent patching protects distributors, not clients.”

The case highlights a structural downside with no straightforward repair.

Disputes between security researchers and main distributors over severity, exploitability, and disclosure have turn into frequent lately, particularly as vulnerability disclosure applications face rising volumes of reviews.

Some open-source maintainers have additionally publicly complained that AI-assisted reviews are overwhelming bug bounty and security triage methods, making it more durable for reputable findings to obtain well timed consideration. Instances the place huge tech ignored patching legitimate flaws regardless of repeated contact by completely different researchers are usually not unusual both.

With no framework that realigns incentives for all events, accountable disclosure dangers changing into a bureaucratic train that serves nobody—least of all of the organizations left uncovered at nighttime.