pac4j JWT Forgery + Copilot Agent Exfiltration: Your Most Urgent Patch Sprint
Two New Vulnerability Classes Demand Immediate Response
Today's patch urgency is driven by two vulnerabilities that represent entirely new attack patterns, not just another round of bug fixes. Together they redefine your most critical exposure this week.
CVE-2026-29000: pac4j JWT Forgery — Maximum Severity, Live PoC
A maximum-severity vulnerability in pac4j, a widely-used open-source Java security library, allows attackers to forge JSON Web Tokens using only publicly available RSA keys. No secrets, no special access, no authentication required. CodeAnt AI discovered the flaw and published a proof-of-concept exploit last week. Patches dropped within two days — but the adoption window is the kill zone.
The critical amplifier: most organizations don't know they depend on pac4j. It's integrated into hundreds of Java packages as a transitive dependency. If you aren't scanning your full dependency tree, you likely don't know if you're exposed. This is precisely the scenario the now-rescinded SBOM mandates were designed to prevent — hidden supply chain dependencies that nobody tracks until they're weaponized.
pac4j is pre-authentication, internet-facing, requires only basic JWT knowledge, and has a live PoC. If it's in your dependency tree, this is a same-day emergency.
CVE-2026-26144: Copilot Agent as Data Exfiltration Tool
An Excel information-disclosure flaw enables Microsoft Copilot Agent to exfiltrate data in a zero-click operation. This isn't another Office bug — it's the first documented weaponization of an AI productivity assistant through a traditional software vulnerability. Your DLP controls almost certainly don't monitor for AI-agent-initiated data movements. The trust boundary between "AI helps employees" and "AI exfiltrates data" just collapsed.
Full Patch Priority Matrix
| CVE | Product | CVSS | Attack Vector | User Interaction |
|---|---|---|---|---|
| CVE-2026-29000 | pac4j (Java) | 10.0 | Network (JWT forgery) | None |
| CVE-2026-28514 | Rocket.Chat | Critical | Network (missing await) | None |
| CVE-2026-26144 | Excel / Copilot | High | Crafted Excel file | Zero-click |
| CVE-2026-26110 | Microsoft Office | High | Preview pane | None |
| CVE-2026-26113 | Microsoft Office | High | Preview pane | None |
The March Patch Tuesday is notable for being the first release in six months with no actively exploited zero-days — but more than half of all 83 vulnerabilities enable privilege escalation, pointing to systemic authorization boundary weaknesses across Microsoft's portfolio. Six defects are rated "more likely to be exploited."
The SBOM Dimension
The Trump administration rescinded Biden-era SBOM and software attestation requirements for federal contractors the same week pac4j proves exactly why transitive dependency visibility matters. As Sonatype CTO Brian Fox noted, the government is "getting tougher on the people exploiting digital systems while getting softer on the conditions that make those systems so easy to exploit." If you were relying on federal mandates to drive vendor transparency, build those requirements into your own contracts now.
What to do
Run `mvn dependency:tree` or equivalent across all Java applications and search for pac4j in direct and transitive dependencies. Patch immediately on any internet-facing application.
Deploy Microsoft March 2026 Patch Tuesday with priority on CVE-2026-26144 (Excel/Copilot), CVE-2026-26110 and CVE-2026-26113 (Office RCE). Disable Outlook preview pane via GPO as interim mitigation.
Audit Copilot Agent permissions and data access scopes. Implement conditional access policies limiting Copilot's reach to non-sensitive data classifications. Configure DLP alerts for AI-initiated data movements.
Add SBOM and software attestation requirements to all new vendor contracts, independent of federal mandates.