Is CVE-2026-40303 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-40303 being exploited in the wild.

How severe is CVE-2026-40303?

High severity, with a CVSS score of 7.5, published 17 April 2026.

Which products and versions are affected?

github.com/openziti/zrok (Go) <= 1.1.11, SEMVER:introduced=0, SEMVER:introduced=0,last_affected=1.1.11; github.com/openziti/zrok/v2 (Go) < 2.0.1, SEMVER:introduced=0,fixed=2.0.1.

Is there a fix for CVE-2026-40303?

Yes. github.com/openziti/zrok/v2 (Go): upgrade to 2.0.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Am I affected by CVE-2026-40303?

Check whether you run github.com/openziti/zrok (Go), github.com/openziti/zrok/v2 (Go) or Netfoundry Zrok 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-2026-40303: zrok: Unauthenticated DoS via unbounded memory allocation in striped session cookie parsing

Q: Is there a fix for CVE-2026-40303?

Yes. github.com/openziti/zrok/v2 (Go): upgrade to 2.0.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

Q: Am I affected by CVE-2026-40303?

Check whether you run github.com/openziti/zrok (Go), github.com/openziti/zrok/v2 (Go) or Netfoundry Zrok 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-2026-40303 · Severity: high · CVSS 7.5 · Published 2026-04-17

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 process-level OOM termination or repeated goroutine panics. Both publicProxy and dynamicProxy are affected. Version 2.0.1 patches the issue.

Technologies: github.com/openziti/zrok (Go), github.com/openziti/zrok/v2 (Go), Netfoundry Zrok. Vendors: Go, Netfoundry.

Quick answers

Is CVE-2026-40303 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-40303 being exploited in the wild.
How severe is CVE-2026-40303?: High severity, with a CVSS score of 7.5, published 17 April 2026.
Which products and versions are affected?: github.com/openziti/zrok (Go) <= 1.1.11, SEMVER:introduced=0, SEMVER:introduced=0,last_affected=1.1.11; github.com/openziti/zrok/v2 (Go) < 2.0.1, SEMVER:introduced=0,fixed=2.0.1.
Is there a fix for CVE-2026-40303?: Yes. github.com/openziti/zrok/v2 (Go): upgrade to 2.0.1 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
Am I affected by CVE-2026-40303?: Check whether you run github.com/openziti/zrok (Go), github.com/openziti/zrok/v2 (Go) or Netfoundry Zrok 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

github.com/openziti/zrok/v2 (Go): upgrade to 2.0.1 or later
```
go get github.com/openziti/zrok/v2@v2.0.1
```

Affected products

github.com/openziti/zrok (Go) <= 1.1.11, SEMVER:introduced=0, SEMVER:introduced=0,last_affected=1.1.11
github.com/openziti/zrok/v2 (Go) < 2.0.1, SEMVER:introduced=0,fixed=2.0.1
Netfoundry Zrok

Identifiers

CVE-2026-40303
GHSA-cpf9-ph2j-ccr9
GO-2026-5329

References

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