Is CVE-2026-63308 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-63308 being exploited in the wild.

How severe is CVE-2026-63308?

Medium severity, with a CVSS score of 4.3, published 17 July 2026.

Which products and versions are affected?

Helm 3.13.0 through 3.21.0, 4.0.0 through 4.2.3.

Is there a fix for CVE-2026-63308?

A patch was published on 2026-07-16: Fix merged into main branch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-63308 attacked?

It is attacked over the network, in a software library.

Am I affected by CVE-2026-63308?

Check whether you run Helm 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-2026-63308: Helm denial of service in Files.Lines template helper

CVE-2026-63308 · Severity: medium · CVSS 4.3 · Published 2026-07-17

Helm, a popular package manager for Kubernetes, contains a flaw that can cause it to crash when processing certain configuration files. An attacker can provide a specially crafted Helm chart containing an empty file which causes the software to fail during installation, upgrades, or testing. This results in a denial of service where users are unable to deploy or manage their applications using the affected tool.

Technologies: Helm. Vendors: Helm.

Quick answers

Is CVE-2026-63308 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-63308 being exploited in the wild.
How severe is CVE-2026-63308?: Medium severity, with a CVSS score of 4.3, published 17 July 2026.
Which products and versions are affected?: Helm 3.13.0 through 3.21.0, 4.0.0 through 4.2.3.
Is there a fix for CVE-2026-63308?: A patch was published on 2026-07-16: Fix merged into main branch Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-63308 attacked?: It is attacked over the network, in a software library.
Am I affected by CVE-2026-63308?: Check whether you run Helm 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.

Technical details

A denial of service vulnerability exists in Helm's template engine within the `Files.Lines` helper in `pkg/engine/files.go`. The root cause is an improper validation of array indices (CWE-129); specifically, the code checks if a file is nil but fails to check if it is a zero-length byte slice before attempting to access the last character to check for a trailing newline. An attacker can include an empty file in a Helm chart, which triggers an "index out of range [-1]" panic during rendering. This affects `helm template`, `install`, `upgrade`, `lint`, and SDK `Engine.Render` operations. The issue is fixed in commit ba6c9a2 and impacts versions 3.13.0 through 4.2.3.

Affected products

Helm Helm 3.13.0 through 3.21.0, 4.0.0 through 4.2.3

Timeline

2026-05-26: disclosed: Vulnerability reported to maintainers via email
2026-07-01: other: Public issue opened on GitHub
2026-07-16: patched: Fix merged into main branch
2026-07-17: advisory: CVE published

References

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