---
title: "CVE-2026-111943: Distrust compromised intermediate certificates in crypto/x509"
url: https://erroneo.us/security/cve/CVE-2026-111943/
description: "CVE-2026-111943 (Go standard library crypto/x509): On most platforms, Go uses the given system root certificates. However, in some narrower cases, the…"
type: vulnerability-record
section: "Security Digest"
date_published: 2026-10-21
date_modified: 2026-10-21
publisher: erroneo.us
author: erroneo.us Security Desk
cve: "CVE-2026-111943"
kev: false
cvss: null
epss: 0.00145
license: All rights reserved. Quote with attribution and a link.
---

# CVE-2026-111943: Distrust compromised intermediate certificates in crypto/x509

**Signal:** Normal patch cycle. No exploitation signal; fix it in your next routine update if you are affected. (Computed from CISA KEV, EPSS and CVSS; not an editorial verdict.)

## Should you act?

- No confirmed exploitation. It is not in CISA’s KEV catalog. That can change quickly after a public write-up; re-check if you are affected.
- EPSS 0.1% , percentile 3: FIRST’s model estimates a 0.1% chance of exploitation activity in the next 30 days, higher than 3% of all scored CVEs (low). EPSS is a probability, not a verdict.
- Editorial verdict: Patch this week. eMudhra CA Key Compromise: Update Non-Browser TLS Clients — Anyone can mint certificates from these broken CA keys, but only clients that skip Certificate Transparency and still trust the emSign root are exposed, and only to an on-path attacker: update those trust bundles this week, build machines first.
- Editorial verdict: Patch this week. Go October 2026 Security Releases: 16 Stdlib Fixes — Rebuild and redeploy Go services with Go 1.27.3 or 1.26.10 this week, starting with internet-facing HTTP/2 servers and reverse proxies; none of these bugs is known to be exploited.

## What it is

On most platforms, Go uses the given system root certificates. However, in some narrower cases, the system trust stores may not be updated without further action. To defend against the narrower set of cases that may remain affected, a denylist was added in crypto/x509 to return an error when calling Verify with any of the known intermediate certificates that are no longer considered to be trustworthy.

## Affected products (CVE record)

- Go standard library crypto/x509: < 1.26.10, 1.27.0-0 < 1.27.3

## Exploitation

- CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
- FIRST EPSS (model of 2026-10-21): 0.14% probability of exploitation activity in the next 30 days; percentile 3.

## Sources

- [CVE.org record CVE-2026-111943](https://www.cve.org/CVERecord?id=CVE-2026-111943)
- [NVD entry CVE-2026-111943](https://nvd.nist.gov/vuln/detail/CVE-2026-111943)
- [go.dev](https://go.dev/cl/851047)
- [go.dev](https://go.dev/issue/82345)
- [groups.google.com](https://groups.google.com/g/golang-announce/c/66pojueaQek)
- [pkg.go.dev](https://pkg.go.dev/vuln/GO-2026-6809)
- [openwall.com](http://www.openwall.com/lists/oss-security/2026/10/20/29)

---
Source page: https://erroneo.us/security/cve/CVE-2026-111943/ · Security Digest: https://erroneo.us/security/ · More: https://erroneo.us/llms.txt