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EUVD-2026-275878

fkie_cve-2026-31976

xygeni-action is the GitHub Action for Xygeni Scanner. On March 3, 2026, an attacker with access to compromised credentials created a series of pull requests (#46, #47, #48) injecting obfuscated shell code into action.yml. The PRs were blocked by branch protection rules and never merged into the main branch. However, the attacker used the compromised GitHub App credentials to move the mutable v5 tag to point at the malicious commit (4bf1d4e19ad81a3e8d4063755ae0f482dd3baf12) from one of the unmerged PRs. This commit remained in the repository's git object store, and any workflow referencing @v5 would fetch and execute it. This is a supply chain compromise via tag poisoning. Any GitHub Actions workflow referencing xygeni/xygeni-action@v5 during the affected window (approximately March 3–10, 2026) executed a C2 implant that granted the attacker arbitrary command execution on the CI runner for up to 180 seconds per workflow run.

GHSA-f8q5-h5qh-33mh — xygeni-action v5 tag poisoned with C2 backdoor

Affected: GitHub Actions: xygeni/xygeni-action

### Description

On March 3, 2026, an attacker with access to compromised credentials created a series of pull requests (#46, #47, #48) injecting obfuscated shell code into `action.yml`. The PRs were blocked by branch protection rules and never merged into the main branch.

However, the attacker used the compromised GitHub App credentials to move the mutable `v5` tag to point at the malicious commit (`4bf1d4e19ad81a3e8d4063755ae0f482dd3baf12`) from one of the unmerged PRs. This commit remained in the repository's git object store, and any workflow referencing `@v5` would fetch and execute it.

The malicious code, disguised as a "scanner version telemetry" step, operates as follows:

1. Registers the CI runner with a C2 server at `91.214.78.178` (via `security-verify.91.214.78.178.nip.io`), transmitting hostname, username, and OS version. 2. Polls the C2 server every 2–7 seconds for 180 seconds, receiving and executing arbitrary shell commands via `eval`. 3. Compresses and base64-encodes command output before exfiltrating it back to the C2 server.

The implant runs silently in the background alongside the legitimate scan, suppresses all errors, skips TLS certificate verification, and uses randomized polling intervals to evade detection.

### Impact

This is a supply chain compromise via tag poisoning. Any GitHub Actions workflow referencing `xygeni/xygeni-action@v5` during the affected window (approximately March 3–10, 2026) executed a C2 implant that granted the attacker arb…