The vulnerability is a supply‑chain compromise caused by an attacker who injected obfuscated shell code into the action.yml of the xygeni/xygeni‑action GitHub Action. By moving the mutable @v5 tag to point at the malicious commit, any workflow that references xygeni/xygeni-action@v5 during the affected window (March 3–10, 2026) will fetch and execute that code. The injected payload is a command‑and‑control implant that grants the attacker arbitrary command execution on the GitHub Actions CI runner for up to 180 seconds on each workflow run. This is an instance of CWE‑506 (Exposed Secret in Source Code) and results in full Remote Code Execution on the build environment.

The affected product is the xygeni-action GitHub Action for the Xygeni Scanner, indicated by the vendor product pair xygeni:xygeni-action. The specific vulnerability impacts the mutable @v5 tag; any workflow that uses xygeni/xygeni-action@v5 during the specified window is at risk. No other versions or tags are listed in the vulnerable commit, so the risk applies exclusively to references that resolve to the malicious v5 tag during that time.

The CVSS score of 9.3 indicates a high‑severity flaw, and the EPSS score of less than 1% suggests limited public exploitation data so far. The vulnerability is not in the CISA KEV catalog. The attack vector is remote, via a compromised GitHub App credential that allowed the attacker to alter tag references. Once a workflow references the poisoned tag, the malicious code executes with the same permissions as the workflow runner, enabling arbitrary command execution. Organizations that use the default @v5 reference during the affected period faced a significant risk of compromise.