CVE-2026-40303: zrok is software for sharing web services, files, and network resources

Q: How do I fix CVE-2026-40303?

zrok: upgrade to 2.0.1. Exact commands for each OS are on this page.

Q: Is CVE-2026-40303 being exploited?

CVE-2026-40303 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-40303 affect?

CVE-2026-40303 affects zrok. Severity is high (CVSS 7.5). zrok is software for sharing web services, files, and network resources. Prior to version 2.0.1, endpoints.GetSessionCookie parses an attacker-supplied cookie chunk count and calls make([]string, count) with no upper bound before any token

Q: How urgent is CVE-2026-40303?

Priority 41/100. High severity; Remotely exploitable, no login, no user action

This month

HIGH 7.5REMOTEUPGRADE

CVE-2026-40303 is a high-severity flaw (CVSS 7.5) affecting zrok. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

zrok is software for sharing web services, files, and network resources. Prior to version 2.0.1, endpoints.GetSessionCookie parses an attacker-supplied cookie chunk count and calls make([]string, count) with no upper bound before any token validation occurs. The function is reached on every request to an OAuth-protected proxy share, allowing an unauthenticated remote attacker to trigger gigabyte-scale heap allocations per request, leading to proc

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	0.5% (top 61%)
CISA exploited list	No
Weakness	CWE-400, CWE-789
Published	2026-04-17
Last modified	2026-10-26

Publisher (CNA): GitHub, Inc. · Vendor: netfoundry

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

Am I affected?

Timeline

2026-04-17 21:16 UTCPublished CVE record published
2026-10-26 22:10 UTCUpdated Record last modified

netfoundry zrok UPGRADE

Affected: < 2.0.1

Fixed in: 2.0.1

Safe to downgrade to: no unaffected older release

1. Check installed version

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

2. UPGRADE to 2.0.1 (Debian / Ubuntu)

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

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade zrok

Note

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

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-2026-40303?

zrok: upgrade to 2.0.1. Exact commands for each OS are on this page.

Is CVE-2026-40303 being exploited?

CVE-2026-40303 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-2026-40303 affect?

CVE-2026-40303 affects zrok. Severity is high (CVSS 7.5). zrok is software for sharing web services, files, and network resources. Prior to version 2.0.1, endpoints.GetSessionCookie parses an attacker-supplied cookie chunk count and calls make([]string, count) with no upper bound before any token

How urgent is CVE-2026-40303?

Priority 41/100. High severity; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-40302 MEDIUM 6.1 UPGRADE zrok is software for sharing web services, files, and network resources
CVE-2026-40304 MEDIUM 5.3 UPGRADE zrok is software for sharing web services, files, and network resources
CVE-2026-42275 HIGH 8.7 UPGRADE zrok is software for sharing web services, files, and network resources
CVE-2026-45568 CRITICAL 9.1 UPGRADE zrok is software for sharing web services, files, and network resources
CVE-2026-45576 HIGH 7.5 UPGRADE zrok is software for sharing web services, files, and network resources

References

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