Is CVE-2026-42507 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-42507 being exploited in the wild.

How severe is CVE-2026-42507?

Informational severity, published 2 June 2026.

Which products and versions are affected?

stdlib (Go) SEMVER:introduced=0,fixed=1.25.11,introduced=1.26.0-0,fixed=1.26.4.

Is there a fix for CVE-2026-42507?

Yes. stdlib (Go): upgrade to 1.26.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-42507 attacked?

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

Am I affected by CVE-2026-42507?

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-2026-42507: Google Go log injection in net/textproto package

CVE-2026-42507 · Severity: info · Published 2026-06-02

A vulnerability in the Go programming language's standard library could allow attackers to manipulate application logs or error messages. By sending specially crafted input to services using the affected library, an attacker can inject misleading text or fake error entries into system logs. This can be used to hide malicious activity or deceive administrators during incident investigations.

Technologies: stdlib (Go). Vendors: Go.

Quick answers

Is CVE-2026-42507 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-42507 being exploited in the wild.
How severe is CVE-2026-42507?: Informational severity, published 2 June 2026.
Which products and versions are affected?: stdlib (Go) SEMVER:introduced=0,fixed=1.25.11,introduced=1.26.0-0,fixed=1.26.4.
Is there a fix for CVE-2026-42507?: Yes. stdlib (Go): upgrade to 1.26.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-42507 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-42507?: 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 1.26.4 or later
```
go get stdlib@v1.26.4
```

Technical details

A log injection vulnerability exists in the Go net/textproto package due to the inclusion of unescaped arbitrary input in returned error strings. Functions such as Reader.ReadCodeLine, Reader.ReadMIMEHeader, and Reader.ReadResponse are affected. An attacker can provide input containing newline characters or other control sequences to inject misleading content into logs or error displays in downstream packages like net/http and net/smtp. This is primarily a public-track issue with limited impact on integrity and availability, but it can be used to obfuscate attacks. The issue is fixed in Go versions 1.25.11 and 1.26.4.

Affected products

Google Go before 1.25.11, 1.26.0 before 1.26.4

Identifiers

CVE-2026-42507
GO-2026-5039

Timeline

2026-05-11: disclosed: Issue opened on GitHub
2026-06-02: advisory: NVD and Go project published advisory

References

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