Kyverno Authorization Bypass via Malformed URL Escapes

Kyverno from 1.19.1 before 1.19.2 contains an authorization bypass vulnerability in the apiCall namespace clamp that allows namespace tenants to issue cross-namespace and cluster-scoped API requests by appending malformed percent-escapes to urlPath. Attackers can create namespaced Policies whose apiCall runs as the admission-controller ServiceAccount to read other namespaces' resources and create mutating webhooks, escalating to cluster admin.

Casky was already ahead

This CVE exploits attack patterns that Casky's 331matched skills already investigate — long before this vulnerability was disclosed. Claude's reasoning model maps these techniques to MITRE ATT&CK, so practitioners who ran these skills have already seen the threat behaviour in their findings.

Analysis

Kyverno versions 1.19.1 before 1.19.2 contain a critical authorization bypass vulnerability that allows namespace-scoped tenants to escape their isolation boundaries and issue cluster-wide API requests. By crafting malformed percent-escape sequences in urlPath parameters, attackers can manipulate the apiCall namespace clamp validation mechanism, enabling unauthorized cross-namespace resource access and webhook injection. This vulnerability is particularly dangerous because it leverages Kyverno's admission controller ServiceAccount—which typically holds elevated privileges—to execute these requests, allowing threat actors to read sensitive resources across namespaces and establish persistence through mutating webhooks. Organizations running vulnerable Kyverno instances face immediate risk of privilege escalation to cluster administrator level, compromising Kubernetes cluster integrity and enabling lateral movement across workloads.

Casky's 331 matching skills use Claude AI with extended reasoning to detect the attack patterns associated with this CVE by correlating evidence across MITRE ATT&CK Initial Access (TA0001) and Execution (TA0006) techniques. Practitioners will see findings flagged for: (1) abnormal apiCall requests containing encoded or malformed escape sequences in policy definitions, (2) namespace-scoped service accounts issuing unexpected cluster-scoped API calls, (3) creation of admission webhooks by low-privilege namespaced policies, and (4) unauthorized cross-namespace resource enumeration patterns. The AI-driven analysis connects these indicators to reveal the authorization bypass chain, helping security teams identify exploitation attempts before privilege escalation occurs and distinguish legitimate policy behavior from attack payloads attempting to escape namespace boundaries.

Live Threat IntelligenceComing soon

Casky Risk Score

—

EPSS Probability

—

Shodan Exposure

—

GreyNoise Signal

—

Composite risk scoring from EPSS, CISA KEV, Shodan, and GreyNoise — 21 security APIs correlated into a single Casky Risk Score. Coming in Casky Pro. Join early access →

331 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-124440.

Abuse of Public-Facing API: Mobile API Abuse

mobile security · low

Run

abusing-dpapi-for-credential-access

red teaming · high

Run

abusing-shadow-credentials-for-privesc

red teaming · high

Run

MITRE ATT&CK Techniques

TA0001 TA0006

Investigate the attack patterns behind CVE-2026-124440

Casky has 331 skills that investigate the attack patterns behind CVE-2026-124440. Run one and get CVSS-scored findings in 3 minutes.

Run the skill that detects this →

X Instagram LinkedIn