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.
CVE-2026-31976
This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit-prediction score not yet available (the EPSS model rescores nightly; freshly-published CVEs typically appear within 48 hours). GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).
- High severity, but no confirmed exploitation yet
No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.
- CVSS v3
- 9.8
- EG Score
- 9.8(low)
- EG Risk
- 49(Track)EG Risk 49/100SSVC: Track
EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).
How it’s computedSeverity98% × 45%Exploitation0% × 40%Automatability30% × 15%Action: Routine — remediate on your standard cadence. - EPSS PROB
- 0%
- EPSS %ILE
- 40%
- KEV
- Not listed
Published
March 11, 2026
Last Modified
June 17, 2026
Advisory Details (2)
Auto-updated Jul 27, 2026xygeni-action v5 tag poisoned with C2 backdoor · Advisory · xygeni/xygeni-action · GitHub
https://github.com/xygeni/xygeni-action/security/advisories/GHSA-f8q5-h5qh-33mhMalicious code · Issue #54 · xygeni/xygeni-action · GitHub
https://github.com/xygeni/xygeni-action/issues/54Weakness Classification(1)
MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.
Data Freshness Timeline
(refreshed 1× in last 7d / 1× in last 30d)
Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.
- 2026-07-27 13:41 UTCEG score recompute
Frequently asked(5)
What is CVE-2026-31976?
When was CVE-2026-31976 disclosed?
Is CVE-2026-31976 actively exploited?
What is the CVSS score of CVE-2026-31976?
How do I remediate CVE-2026-31976?
Dependency Blast Radius
Explore the affected products and dependency analysis for CVE-2026-31976
Is Your Infrastructure Affected by CVE-2026-31976?
EchelonGraph automatically scans your cloud infrastructure and maps CVE exposure using blast radius analysis.