Affected Systems
eMudhra intermediate certificates issued April 2025 using P-384 keys with values <256. Affects systems using Mozilla NSS, Go (pre-1.27.3/1.26.10), Python certifi, Rust webpki, Electron, and other software with embedded certificate stores. Firefox, Chrome, Safari, and major Linux distributions have deployed blocks.
Exploitation Status
No evidence of active exploitation. Private keys were recoverable since April 2025 via brute force of 256 values. Proof-of-concept key (value=4) published on GitHub. Certificates revoked October 17, 2026.
Business Impact
Compromised intermediate CA certificates could allow attackers to forge trusted TLS certificates for any domain, enabling man-in-the-middle attacks and impersonation of legitimate websites. Risk highest for systems that do not check CRLs/OCSP or use outdated certificate bundles. eMudhra claims most intermediates were unused in production, but exposure window was 18 months. macOS /usr/bin/curl does not check revocation and remains vulnerable until patched.
Urgency
🟠Within 24 hours
Recommended Actions
- Update certificate bundles immediately: Ubuntu ca-certificates 20260816ubuntu0.*, Alpine 20261020-r0, Arch ca-certificates-mozilla 3.131.1-1, NSS 3.131.1, Python certifi 2026.10.19, Rust rustls-webpki 0.103.16
- Patch Go to 1.27.3 or 1.26.10 (CVE-2026-111943) for applications using Go's crypto/x509 package
- Test internal systems and appliances using Dennis Jackson's incident tracking site test endpoints to identify software still trusting revoked eMudhra intermediates
- Review TLS inspection proxies, load balancers, and embedded systems for stale certificate stores; prioritize devices that do not auto-update or check revocation
- Monitor for unexpected certificate issuance under eMudhra G3 root in Certificate Transparency logs from April 2025 to October 2026 as forensic indicator