CRI-O Container Environment Variable Injection Bypass

A flaw was found in CRI-O. The fix for a previous vulnerability (CVE-2022-4318) was incorrect, allowing it to be bypassed. An attacker capable of setting environment variables on a container can inject a newline character into the HOME environment variable. This issue allows the addition of arbitrary lines into /etc/passwd by use of a specially crafted environment variable.

Casky was already ahead

This CVE exploits attack patterns that Casky's 322matched 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

CVE-2026-15809 represents a critical container security failure in CRI-O where a previously patched vulnerability (CVE-2022-4318) remains exploitable through environment variable manipulation. An attacker with container-level privileges can inject newline characters into the HOME environment variable, enabling arbitrary writes to /etc/passwd and potential privilege escalation or lateral movement within containerized environments. This vulnerability affects organizations running CRI-O as their container runtime—particularly Kubernetes clusters—and is particularly dangerous because it undermines the container isolation model that these platforms depend on for multi-tenant security.

Casky's 322 mapped skills leverage Claude AI's extended reasoning to identify the attack patterns associated with TA0001 (Initial Access) and TA0043 (Reconnaissance) techniques by correlating CWE-134 (Use of Externally-Controlled Format String) and CWE-116 (Improper Encoding or Escaping of Output) indicators. Practitioners using Casky would detect suspicious findings including: environment variable anomalies with embedded newline sequences, unauthorized /etc/passwd modifications traced to container processes, and privilege escalation attempts following container creation. The platform's skill mapping would flag the root cause—inadequate input sanitization on environment variables during container initialization—allowing security teams to distinguish this bypass from other container escapes and prioritize remediation of CRI-O instances in their infrastructure.

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Casky Risk Score

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EPSS Probability

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Shodan Exposure

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GreyNoise Signal

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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 →

322 Casky skills cover this attack pattern

These skills use Claude AI's reasoning model to surface findings in the same attack categories as CVE-2026-15809.

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 TA0043

Investigate the attack patterns behind CVE-2026-15809

Casky has 322 skills that investigate the attack patterns behind CVE-2026-15809. Run one and get CVSS-scored findings in 3 minutes.

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