Trivy Action runs Trivy as GitHub action to scan a Docker container image for vulnerabilities. A command injection vulnerability exists in "aquasecurity/trivy-action" versions 0.31.0 through 0.33.1 due to improper handling of action inputs when exporting environment variables. The action writes "export VAR=<input>" lines to "trivy_envs.txt" based on user-supplied inputs and subsequently sources this file in "entrypoint.sh". Because input values are written without appropriate shell escaping, attacker-controlled input containing shell metacharacters (e.g., "$(...)", backticks, or other command substitution syntax) may be evaluated during the sourcing process. This can result in arbitrary command execution within the GitHub Actions runner context. Version 0.34.0 contains a patch for this issue. The vulnerability is exploitable when a consuming workflow passes attacker-controlled data into any action input that is written to "trivy_envs.txt". Access to user input is required by the malicious actor. Workflows that do not pass attacker-controlled data into "trivy-action" inputs, workflows that upgrade to a patched version that properly escapes shell values or eliminates the "source ./trivy_envs.txt" pattern, and workflows where user input is not accessible are not affected.