Is CVE-2026-39820 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-39820 being exploited in the wild.

How severe is CVE-2026-39820?

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-2026-39820?

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-2026-39820 attacked?

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

Am I affected by CVE-2026-39820?

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-2026-39820: Go net/mail denial of service in email and date parsing

CVE-2026-39820 · Severity: high · CVSS 7.5 · Published 2026-05-07

A vulnerability in the Go programming language's standard library can allow an attacker to crash or slow down applications that process email addresses or dates. By sending specially crafted email headers, an attacker can force the system to consume excessive processor power and memory. This can lead to a denial-of-service (DoS) condition, making the affected service unavailable to legitimate users.

Technologies: stdlib (Go). Vendors: Go.

Quick answers

Is CVE-2026-39820 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-39820 being exploited in the wild.
How severe is CVE-2026-39820?: 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-2026-39820?: 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-2026-39820 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-39820?: 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 denial of service vulnerability exists in the Go standard library's net/mail package. The functions ParseAddress, ParseAddressList, and ParseDate (and their associated methods) fail to properly handle certain malformed inputs, leading to quadratic complexity during comment consumption. An unauthenticated remote attacker can exploit this by providing specially crafted email headers, resulting in excessive CPU consumption and memory allocation. The issue is tracked in the Go project as issue 78566 and has been patched in Go versions 1.25.10 and 1.26.3.

Affected products

Google Go before 1.25.10, from 1.26.0-0 before 1.26.3
Red Hat OpenShift Service Mesh 3.0, 3.1, 3.2, 3.3

Identifiers

CVE-2026-39820
GO-2026-4986

Timeline

2026-04-07: disclosed: Issue opened in Go project repository
2026-05-07: advisory: Published in Go vulnerability database and NVD
2026-06-29: patched: Red Hat released security advisories for affected products

References

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