CVE-2026-111943

Distrust compromised intermediate certificates in crypto/x509

No known exploitation. EPSS puts it in the 3rd percentile. Fixed versions are out.

CVSS —Not scored EPSS percentile3rd0.1% chance in 30 days CISA KEVNot listedNo confirmed exploitation
No public exploit known Fix1 product2 fixed builds listed below

Published 2026-10-21Updated 2026-10-22Sources: CVE.org, NVD

NVD CVE.org

What to do

Find your product and version, then upgrade to the build on the right.

Go standard library crypto/x509Affected: < 1.26.10Upgrade to: 1.26.10Affected: ≥ 1.27.0-0, < 1.27.3Upgrade to: 1.27.3Stated by: CVE record

Versions as the sources state them. Full version matrix after sign-in

Steps

Written by AI from the record

Check whether any of your internal tools, services, or products are built with the Go programming language and use its crypto/x509 package for certificate verification.
Ask your developer or vendor whether they rely on crypto/x509 and if so, which Go version is in use.
Upgrade to Go version 1.26.10 or 1.27.3, whichever matches your current release branch.
Rebuild and redeploy any affected applications after upgrading.
Confirm with your vendor that no further action is needed if they manage the Go runtime on your behalf.

go get go@1.27.3

Usually a quick update

Check it yourselfA free OpenVAS check exists for this CVE. Run it against your hosts.Is your organisation exposed?Request an assessment to establish which checks fit your systems.

Coverage timeline

3 publishers

Cisco Talos issued an advisory regarding eight compromised eMudhra intermediate CA certificates caused by weak key generation, prompting browser vendors and Go language runtime to block the keys and release updates.
as reported · Oct 21, 2026·Cisco Talos summary
Major browsers and software vendors released updates to block eight compromised eMudhra intermediate CA certificates after researchers demonstrated their private keys were trivially recoverable.
as reported · Oct 21, 2026·BleepingComputer summary

Sourced from public security reporting — each date is when it was published, not when it happened.

What it is

From the CVE record

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.

In plain language

Written by AI from the record

A Go programming library used to verify website and software identities now blocks a handful of known-compromised certificates, and while attackers aren't known to be exploiting this, businesses that use Go software should update soon.

Go's crypto/x509 package adds a hardcoded denylist of eMudhra intermediate certificates known to be compromised, so Verify() now rejects them even when a host's OS trust store hasn't yet removed them, closing a gap for systems with outdated trust stores.

If you're affected

Spoofed identity acceptance risk
Man-in-the-middle exposure
Compliance/trust validation failure

What is it

Think of this like a bouncer's list of banned IDs. Some digital 'ID cards' (certificates) used to prove a website or service is legitimate were stolen or compromised, and this update adds them to a built-in blocklist so your software won't trust them even if your computer's main list hasn't caught up yet.

Who is affected

This matters to you if any software your business builds, runs, or buys was written using the Go programming language and relies on its crypto/x509 package to check certificates — for example, internal tools, APIs, or custom applications. It affects any such system by default, since the check happens automatically whenever certificate verification runs, with no login or special conditions needed to trigger it.

How urgent is it

There is no evidence of attackers exploiting this flaw, and it is not on any confirmed-exploitation list — this is a defensive update, not a reaction to active attacks. Still, because the underlying certificates were genuinely compromised and some systems may not have removed them through normal OS updates, you should plan to update within a reasonable window rather than treat it as optional. This is a moderate-priority fix, not an emergency.

What to do — in detail

Identify all services, internal tools, and build pipelines using the Go toolchain, and determine which ones import crypto/x509 for certificate verification (either directly or via a dependency).
Check the Go version in use: go version. Versions prior to 1.26.10 (1.26.x branch) or 1.27.3 (1.27.x branch) are affected.
Upgrade the Go toolchain to 1.26.10 or 1.27.3 depending on your branch, then rebuild all affected binaries — this is a toolchain/runtime fix, not a dependency bump, so recompilation is required to pick up the denylist.
There is no clean workaround short of upgrading, since the fix adds a hardcoded denylist inside crypto/x509's Verify logic; removing the compromised eMudhra intermediates from your OS/system trust store manually is a partial mitigation if you cannot rebuild immediately.
No CISA KEV listing and no due date apply here; this is a preventive hardening update following a public disclosure (researcher 'Wayne', Oct 17) and vendor revocation by eMudhra, not an active-exploitation patch.
Monitor Go's official advisories and your CI/CD pipeline's Go version pinning to ensure future builds pick up the fix automatically.

Technical context

Weakness: improper trust validation of compromised intermediate CA certificates due to reliance on possibly-stale system trust stores. Attack vector: network, no authentication or user interaction required, reachable by default wherever certificate verification occurs (e.g., TLS handshakes). No exploit code is publicly known, and the vulnerability is not listed in CISA's Known Exploited Vulnerabilities catalog. Press coverage is limited to advisory/disclosure reporting (researcher 'Wayne', Oct 17; eMudhra revocation; browser vendors already blocked the certificates independently). Fixed in Go 1.26.10 and 1.27.3 via a hardcoded denylist in crypto/x509.Verify.

This is a general assessment based on public vulnerability data. It does not account for your specific infrastructure — when in doubt, consult a security specialist.

Exploitation

Where each signal puts this CVE on the scale from published to confirmed exploited.

EPSS3rd

CISA KEV

Not in the catalog. CISA has not confirmed exploitation.

Public exploits

No public exploit or proof of concept found in the sources we track.

EPSS

0.1% chance of exploitation activity in the next 30 days, which ranks it in the 3rd percentile of scored CVEs.

Exploit Prediction Scoring System, FIRST.org. A probability, not a confirmation.

Lifecycle

5 events over 5 days, from the signal feeds we watch.

2026-10-26Analysis publishedAttacked from all sides? PHP, Laravel, Node.js and a CA with a key of "4": what is real
2026-10-22OpenVAS check addedrecord updated
2026-10-21Publishedrecord updated

Affected products

Go standard libraryoss-project · USaka golang standard library, html/template, crypto/x509, net/http
- crypto/x509LibraryLibraryOSS Libraries / generic-library

Sources

References in the record

And 2 more references. See all after sign-in

In the news

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We'll flag the next CVE, public exploit or patch for Crypto/x509, not every advisory.

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