Is CVE-2026-33811 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-33811 being exploited in the wild.

How severe is CVE-2026-33811?

High severity, with a CVSS score of 7.5, published 7 May 2026.

Which products and versions are affected?

stdlib (Go) SEMVER:introduced=0,fixed=1.25.10,introduced=1.26.0-0,fixed=1.26.3.

Is there a fix for CVE-2026-33811?

Yes. stdlib (Go): upgrade to 1.26.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-33811 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-33811?

Check whether you run stdlib (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-33811: Go net package double-free in cgo DNS resolver

CVE-2026-33811 · Severity: high · CVSS 7.5 · Published 2026-05-07

A vulnerability in the Go programming language's networking library can cause applications to crash when they attempt to resolve certain domain names. This occurs when a malicious or malformed DNS response contains an excessively long CNAME record, leading to a memory error that terminates the program. This can be used by attackers to cause a denial-of-service, potentially taking down critical web services or internal applications that rely on Go's standard networking features.

Technologies: stdlib (Go). Vendors: Go.

Quick answers

Is CVE-2026-33811 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-33811 being exploited in the wild.
How severe is CVE-2026-33811?: High severity, with a CVSS score of 7.5, published 7 May 2026.
Which products and versions are affected?: stdlib (Go) SEMVER:introduced=0,fixed=1.25.10,introduced=1.26.0-0,fixed=1.26.3.
Is there a fix for CVE-2026-33811?: Yes. stdlib (Go): upgrade to 1.26.3 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-33811 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-33811?: Check whether you run stdlib (Go) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

stdlib (Go): upgrade to 1.26.3 or later
```
go get stdlib@v1.26.3
```

Technical details

A double-free vulnerability (CWE-415) exists in the Go standard library 'net' package when using the cgo-based DNS resolver. The flaw is located within the LookupCNAME and Resolver.LookupCNAME functions. When the resolver processes a specially crafted, excessively long CNAME DNS response, it incorrectly manages C memory pointers, leading to a double-free condition and a subsequent process crash. This is a remote attack vector requiring no authentication, as an attacker only needs to control or spoof a DNS response sent to the vulnerable application. The issue is resolved in Go versions 1.25.10 and 1.26.3.

Affected products

Google Go before 1.25.10, 1.26.0 before 1.26.3
Red Hat Red Hat Hardened Images 1
Red Hat Red Hat OpenShift Service Mesh 3.0, 3.1, 3.2, 3.3

Identifiers

CVE-2026-33811
GO-2026-4981

Timeline

2026-04-16: disclosed: Issue opened on Go GitHub repository
2026-05-07: advisory: Go vulnerability report GO-2026-4981 published
2026-05-07: patched: Fixes released in Go 1.25.10 and 1.26.3
2026-06-04: patched: Red Hat released security advisories for affected products

References

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