# CVE-2026-47078: Relative path traversal in zip:unzip/zip:extract via check_dir_level depth-counter bypass

> Attackers can write files outside the intended directory using crafted zip archives due to a validation bypass in Erlang OTP's zip module.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:L/SC:N/SI:L/SA:L`)
- **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:** 27 Jul 2026
- **Updated:** 24 Sep 2026
- **Also known as:** DEBIAN-CVE-2026-47078, EEF-CVE-2026-47078, GHSA-rf72-wp7h-jg3x, UBUNTU-CVE-2026-47078

## What is CVE-2026-47078?

CVE-2026-47078 is a medium-severity path traversal vulnerability in Erlang OTP, published on 27 Jul 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

Relative Path Traversal vulnerability in Erlang OTP (stdlib zip module) allows writing files outside the intended extraction directory via a crafted zip archive.

zip:unzip/1,2 and zip:extract/1,2 validate entry paths using zip:check_dir_level/2, which tracks directory depth as a running integer counter: .. decrements it, normal path components increment it. The caller rejects only paths where the final counter value is less than zero. A path such as ../x/y causes the counter to go negative mid-traversal then recover to zero, passing validation while resolving to a location outside the extraction directory when joined with the current working directory via add_cwd.

This vulnerability is associated with program file lib/stdlib/src/zip.erl.

This issue affects OTP from OTP 27.1 before OTP 27.3.4.15, OTP 28.5.0.4, and OTP 29.0.4, corresponding to stdlib from 6.1 before 6.2.2.4, 7.3.0.1, and 8.0.3.

Weakness: CWE-23 (Relative Path Traversal)

## Which versions are affected by CVE-2026-47078?


## How do I fix CVE-2026-47078?

Upgrade to a fixed version.

## Is CVE-2026-47078 being exploited?

There is no known exploitation of CVE-2026-47078 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-47078 and fix it if it is affected.

What it is: CVE-2026-47078 is a medium-severity path traversal vulnerability in Erlang OTP, published on 27 Jul 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: There is no known exploitation of CVE-2026-47078 in the wild and no public exploit code.

Affected product: Erlang OTP. 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-2026-47078/ (Markdown: https://insights.sbomify.com/CVE-2026-47078/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-47078
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-47078
- OSV: https://osv.dev/vulnerability/CVE-2026-47078

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From sbomify Insights: https://insights.sbomify.com/CVE-2026-47078/
Summaries are generated and may contain mistakes; the official description above is the record.