# CVE-2026-42499: Google Go net/mail denial of service in consumePhrase

Source: https://junglewise.ai/threats/cve-2026-42499-google-go-net-mail-denial-of-service-in-consumephrase  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-05-07. Updated: 2026-06-30  
License: CC BY 4.0 with a link back

CVE-2026-42499 · Severity: high · CVSS 7.5 · Published 2026-05-07

A vulnerability in the Go programming language's email parsing library can allow an attacker to crash or slow down applications that process email addresses. By sending a specially crafted, complex email address, an attacker can trigger an inefficient computing process that consumes excessive system resources. This can lead to a denial-of-service (DoS) condition, making the affected service unavailable to legitimate users.

Technologies: [stdlib (Go)](https://junglewise.ai/threats/technologies/go-stdlib). Vendors: [Go](https://junglewise.ai/threats/vendors/go).

## Quick answers

**Is CVE-2026-42499 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-42499 being exploited in the wild.

**How severe is CVE-2026-42499?** 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-2026-42499?** 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-2026-42499 attacked?** It is attacked over the network, in a software library.

**Am I affected by CVE-2026-42499?** 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

  ```sh
  go get stdlib@v1.26.3
  ```


## Technical details

A denial of service (DoS) vulnerability exists in the Go standard library's 'net/mail' package due to quadratic string concatenation in the 'consumePhrase' function. When parsing email addresses according to RFC 5322, certain pathological inputs can trigger inefficient resource consumption. An unauthenticated remote attacker can exploit this by providing a specially crafted email address to functions such as ParseAddress or AddressList. This results in a CPU-based denial of service. The issue is fixed in Go versions 1.25.10 and 1.26.3.

## Affected products

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

## Identifiers

- CVE-2026-42499
- GO-2026-4977

## Timeline

- 2026-04-28: disclosed: Issue opened on Go GitHub repository
- 2026-05-07: advisory: NVD and Go vulnerability report published
- 2026-06-29: patched: Red Hat released security advisories for OpenShift Service Mesh

## References

- [https://pkg.go.dev/](https://pkg.go.dev/)
- [https://go.dev/cl/771520](https://go.dev/cl/771520)
- [https://go.dev/issue/78987](https://go.dev/issue/78987)
- [https://groups.google.com/g/golang-announce/c/qcCIEXso47M](https://groups.google.com/g/golang-announce/c/qcCIEXso47M)
- [https://pkg.go.dev/vuln/GO-2026-4977](https://pkg.go.dev/vuln/GO-2026-4977)
- [https://access.redhat.com/errata/RHSA-2026:33120](https://access.redhat.com/errata/RHSA-2026:33120)
- [https://access.redhat.com/errata/RHSA-2026:33123](https://access.redhat.com/errata/RHSA-2026:33123)

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