CVE-2026-63308
Description
A flaw was found in Helm. A remote attacker can exploit a denial of service vulnerability by including zero-length byte slices, such as empty files, within Helm chart files. This can trigger an index out of range panic in the Files.Lines template helper, leading to deterministic render failures during template, installation, upgrade, linting, and SDK Engine.Render operations.
Statement
A denial of service flaw was found in Helm, a package manager for Kubernetes. The Files.Lines template helper in the chart-rendering engine does not check that an included chart file contains at least one line before indexing into it. A chart that contains a zero-length file causes an index-out-of-range panic, which stops the current template, install, upgrade, lint, or SDK Engine.Render operation from completing.
Red Hat rates this issue as having a Moderate impact. Exploitation requires that a user or automated pipeline process a chart containing an empty file with Helm; the crafted chart must first be supplied by an untrusted chart source or repository. Because the panic only terminates the local Helm invocation rather than a long-running service, and does not expose or corrupt data, Red Hat assesses the impact to availability as Low, which is why Red Hat's score differs from the "High" availability impact used by NVD.
Mitigation
There is no configuration change that fully prevents this issue; upgrading to a fixed version of Helm resolves it. As a workaround, verify that Helm charts obtained from third-party or untrusted sources do not contain zero-byte files before processing them with `helm template`, `helm install`, `helm upgrade`, `helm lint`, or the SDK Engine.Render function.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.3 | 6.5 | 4.3 |
| Attack Vector | Network | Network | Network |
| Attack Complexity | Low | Low | Low |
| Privileges Required | None | None | None |
| User Interaction | Required | Required | Required |
| Scope | Unchanged | Unchanged | Unchanged |
| Confidentiality | None | None | None |
| Integrity Impact | None | None | None |
| Availability Impact | Low | High | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
NVD: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
Understanding the Weakness (CWE)
Integrity,Availability
Technical Impact: DoS: Crash, Exit, or Restart
Use of an index that is outside the bounds of an array will very likely result in the corruption of relevant memory and perhaps instructions, leading to a crash, if the values are outside of the valid memory area.
Integrity
Technical Impact: Modify Memory
If the memory corrupted is data, rather than instructions, the system will continue to function with improper values.
Confidentiality,Integrity
Technical Impact: Modify Memory; Read Memory
Use of an index that is outside the bounds of an array can also trigger out-of-bounds read or write operations, or operations on the wrong objects; i.e., "buffer overflows" are not always the result. This may result in the exposure or modification of sensitive data.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If the memory accessible by the attacker can be effectively controlled, it may be possible to execute arbitrary code, as with a standard buffer overflow and possibly without the use of large inputs if a precise index can be controlled.
Integrity,Availability,Confidentiality
Technical Impact: DoS: Crash, Exit, or Restart; Execute Unauthorized Code or Commands; Read Memory; Modify Memory
A single fault could allow either an overflow (CWE-788) or underflow (CWE-786) of the array index. What happens next will depend on the type of operation being performed out of bounds, but can expose sensitive information, cause a system crash, or possibly lead to arbitrary code execution.
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