CVE-2026-42499: Pathological inputs could cause DoS through consumePhrase when parsing an email address according to RFC 5322.

This month

HIGH 7.5REMOTEUPGRADE

CVE-2026-42499 is a high-severity flaw (CVSS 7.5) affecting go. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Pathological inputs could cause DoS through consumePhrase when parsing an email address according to RFC 5322.

Why this priority

High severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.8% (top 44%)
CISA exploited list	No
Weakness	CWE-1046
Published	2026-05-07
Last modified	2026-10-26

Publisher (CNA): Go Project · Vendor: golang

Last updated 2026-10-26 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-07 20:16 UTCPublished CVE record published
2026-10-26 00:10 UTCUpdated Record last modified

golang go UPGRADE

Affected: < 1.25.10 · >= 1.26.0 and < 1.26.3

Fixed in: 1.25.10, 1.26.3

Safe to downgrade to: a release before 1.26.0

1. Check installed version

apt-cache policy go || rpm -q go || go --version

2. UPGRADE to 1.25.10 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade go

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade go

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 1.26.0 (Debian / Ubuntu)

apt-cache madison go sudo apt install go=<VERSION_BEFORE_1.26.0> sudo apt-mark hold go

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list go sudo dnf downgrade go-<VERSION_BEFORE_1.26.0> sudo dnf versionlock add go

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-42499?

go: upgrade to 1.25.10, 1.26.3. Exact commands for each OS are on this page.

Is CVE-2026-42499 being exploited?

CVE-2026-42499 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-42499 affect?

CVE-2026-42499 affects go. Severity is high (CVSS 7.5). Pathological inputs could cause DoS through consumePhrase when parsing an email address according to RFC 5322.

How urgent is CVE-2026-42499?

Priority 45/100. High severity; Remotely exploitable, no login, no user action

Software pages

Go (Golang) vulnerabilities

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References

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