CVE-2026-111943
Go crypto/x509 trusts compromised eMudhra intermediate CAs
Go before 1.26.10 and 1.27.3 can accept chains through eight compromised eMudhra intermediate CAs. Update Go and rebuild. Not in CISA KEV; no known attacks.
By ThreatWire Desk · Published 21 Oct 2026 · Updated 27 Oct 2026
- CVSS
- Unknown
- Vector
- Not recorded
- Class
- Other
- Status
- PoC Available
- KEV
- Not in CISA KEV
- 0-day
- No
- Vendor
- Go
- Products
- Go standard library (crypto/x509)
- Affected
- crypto/x509 in Go before 1.26.10, and Go 1.27.0-0 before 1.27.3.
- Fixed
- Go 1.26.10 and Go 1.27.3 (released 19 October 2026). Binaries must be rebuilt with a fixed toolchain.
- CWE
- CWE-299
- Published
- 21 Oct 2026
- Updated
- 27 Oct 2026
The status above is the claim. Links do not upgrade it.
What happened
Go programs built with an unpatched toolchain can trust TLS chains that pass through eight compromised eMudhra intermediate CAs. Anyone can recover those CAs' private keys.
Go fixed it by adding a denylist to crypto/x509. Verify now rejects any chain that contains one of these intermediates. Go 1.27.3 and 1.26.10 shipped the fix on 19 October 2026. The CVE record was published on 21 October 2026.
Go files the weakness as CWE-299, Improper Check for Certificate Revocation. NVD lists the record as awaiting analysis and shows no CVSS score.
Who is affected
Go uses the system trust store on most platforms. The denylist covers the narrower cases where that store has not been updated, Go says.
Go programs that verify certificates with crypto/x509 and were built with Go before 1.26.10, or 1.27.x before 1.27.3. Go compiles the standard library into each binary, so updating the toolchain alone is not enough.
What is confirmed
The Go vulnerability report GO-2026-6809 lists the affected and fixed versions. CISA's Known Exploited Vulnerabilities catalog does not list this CVE (checked 27 October 2026).
Public tools already recover the eMudhra keys and sign test certificates. Some say unpatched Go accepts the result. We read them without running them, and none targets this CVE id specifically. So we mark a public PoC but give no link.
What is not confirmed
No vendor reports real-world misuse of the keys. Go does not publish a severity rating, and NVD has not scored the record.
What to do
- Upgrade Go to 1.27.3 or 1.26.10, or later.
- Rebuild and redeploy every Go binary and container that verifies TLS.
- Ask vendors of Go-based tools for builds made with a fixed toolchain.
Background on the full incident: eMudhra blames a script error for CA keys that anyone can recover.