# CVE-2026-43965: Path Traversal in build/packages/packages.toml Allows Arbitrary Directory Deletion

> Attackers can delete arbitrary directories by tricking users into downloading dependencies from a project with a malicious packages.toml file.

- **Severity:** Medium 5.6 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:N/VI:N/VA:H/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:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 2 Jun 2026
- **Updated:** 8 Sep 2026
- **Also known as:** EEF-CVE-2026-43965, GHSA-jqvf-f6p2-wrv3

## What is CVE-2026-43965?

CVE-2026-43965 is a medium-severity path traversal vulnerability in Gleam, published on 2 Jun 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

Path traversal vulnerability in Gleam's dependency management allows arbitrary directory deletion via malicious build/packages/packages.toml content.

Package keys read from build/packages/packages.toml by LocalPackages::read_from_disc are passed without validation to paths.build_packages_package(), which constructs a filesystem path by joining the project build directory with the attacker-controlled key. The resulting path is then passed to fs::delete_directory (which calls remove_dir_all). No check is performed to ensure the path remains within the intended build/packages/ directory. Both absolute paths and relative traversal sequences (e.g. ../) are accepted as package keys, allowing deletion of arbitrary directories.

An attacker who can cause a victim to run gleam deps download on a project containing a malicious build/packages/packages.toml (e.g. by committing the normally-gitignored file to a repository) can cause arbitrary directories on the victim's system to be recursively deleted.

This issue affects Gleam from 0.18.0-rc1 until 1.17.0.

Weakness: CWE-22 (Improper Limitation of a Pathname to a Restricted Directory)

## Which versions are affected by CVE-2026-43965?


## How do I fix CVE-2026-43965?

Apply the vendor's patch.

## Is CVE-2026-43965 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-43965 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-43965 and fix it if it is affected.

What it is: CVE-2026-43965 is a medium-severity path traversal vulnerability in Gleam, published on 2 Jun 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-43965 exists.

Affected product: Gleam. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-43965/ (Markdown: https://insights.sbomify.com/CVE-2026-43965/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-43965
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-43965
- OSV: https://osv.dev/vulnerability/CVE-2026-43965

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-43965/
Summaries are generated and may contain mistakes; the official description above is the record.