# CVE-2026-100838: Contrast before 1.19.1 CopyFile Policy Symlink Subversion

> A malicious host process can overwrite guest filesystem files via symlink subversion in Contrast, leading to guest takeover and data disclosure.

- **Severity:** High 8.6 (`CVSS:4.0/AV:A/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 27 Sep 2026
- **Updated:** 8 Oct 2026
- **Also known as:** GHSA-h734-rggh-79xq, GHSA-rh99-wc69-c255, GO-2026-5624

## What is CVE-2026-100838?

CVE-2026-100838 is a high-severity path traversal vulnerability in edgelesssys contrast, published on 27 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

Contrast is a confidential-computing runtime for Kubernetes. In versions before 1.19.1, the Kata agent policies generated by the Contrast CLI contained a flaw in the CopyFile verification that allowed arbitrary writes to the guest root filesystem. A malicious process on the untrusted host able to connect to the Kata agent VSOCK could issue a series of CopyFile requests to overwrite security-critical files in the guest or trick the workload into disclosing sensitive data, effectively amounting to a full guest takeover. Users unable to upgrade can apply an equivalent rego policy fix passed to 'contrast generate --policy'.

Weakness: CWE-59 (Improper Link Resolution Before File Access)

## Which versions are affected by CVE-2026-100838?

3 open source packages ship an affected version, including github.com/edgelesssys/contrast.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/edgelesssys/contrast` | Go | All versions | 1.19.1 |
| `github.com/edgelesssys/contrast` | Go | All versions | 1.19.1 |
| `github.com/edgelesssys/contrast` | Go | All versions | 1.19.1 |

## How do I fix CVE-2026-100838?

Upgrade github.com/edgelesssys/contrast to 1.19.1 or later.

## Is CVE-2026-100838 being exploited?

There is no known exploitation of CVE-2026-100838 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-100838 and fix it if it is affected.

What it is: CVE-2026-100838 is a high-severity path traversal vulnerability in edgelesssys contrast, published on 27 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-100838 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/edgelesssys/contrast (Go): affected all versions; fixed in 1.19.1
- github.com/edgelesssys/contrast (Go): affected all versions; fixed in 1.19.1
- github.com/edgelesssys/contrast (Go): affected all versions; fixed in 1.19.1

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-100838/ (Markdown: https://insights.sbomify.com/CVE-2026-100838/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-100838
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-100838
- OSV: https://osv.dev/vulnerability/CVE-2026-100838

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-100838/
Summaries are generated and may contain mistakes; the official description above is the record.