CVE-2026-27143: Arithmetic over induction variables in loops were not correctly checked for underflow or overflow

This month

CRITICAL 9.8REMOTEUPGRADE

CVE-2026-27143 is a critical-severity flaw (CVSS 9.8) affecting go. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Arithmetic over induction variables in loops were not correctly checked for underflow or overflow. As a result, the compiler would allow for invalid indexing to occur at runtime, potentially leading to memory corruption.

Why this priority

Critical severity
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	9.8 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.5% (top 55%)
CISA exploited list	No
Published	2026-04-08
Last modified	2026-07-25

Publisher (CNA): Go Project · Vendor: golang

Last updated 2026-07-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-04-08 02:16 UTCPublished CVE record published
2026-07-25 11:10 UTCUpdated Record last modified

golang go UPGRADE

Affected: < 1.25.9 · >= 1.26.0 and < 1.26.2

Fixed in: 1.25.9, 1.26.2

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 1.25.9 (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-2026-27143?

go: upgrade to 1.25.9, 1.26.2. Exact commands for each OS are on this page.

Is CVE-2026-27143 being exploited?

CVE-2026-27143 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-2026-27143 affect?

CVE-2026-27143 affects go. Severity is critical (CVSS 9.8). Arithmetic over induction variables in loops were not correctly checked for underflow or overflow. As a result, the compiler would allow for invalid indexing to occur at runtime, potentially leading to memory corruption.

How urgent is CVE-2026-27143?

Priority 51/100. Critical severity; Remotely exploitable, no login, no user action

Software pages

Go (Golang) vulnerabilities

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References

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