# CVE-2026-21620: TFTP Path Traversal

> Attackers can exploit relative path traversal in Erlang OTP's TFTP module to read or modify arbitrary files on the server.

- **Severity:** Low 2.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 20 Feb 2026
- **Updated:** 24 Jul 2026
- **Also known as:** AZL-78278, AZL-78285, DEBIAN-CVE-2026-21620, EEF-CVE-2026-21620, GHSA-hmrc-prh3-rpvp, OESA-2026-2703, OESA-2026-2705, UBUNTU-CVE-2026-21620

## What is CVE-2026-21620?

CVE-2026-21620 is a low-severity path traversal vulnerability in Erlang OTP, published on 20 Feb 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Relative Path Traversal, Improper Isolation or Compartmentalization vulnerability in erlang otp erlang/otp (tftp_file modules), erlang otp inets (tftp_file modules), erlang otp tftp (tftp_file modules) allows Relative Path Traversal. This vulnerability is associated with program files lib/tftp/src/tftp_file.erl, src/tftp_file.erl.

This issue affects OTP from OTP 17.0 before OTP 28.3.2, OTP 27.3.4.8 and OTP 26.2.5.17, corresponding to tftp from 1.0 before 1.2.4, 1.2.2.1 and 1.1.1.1; also inets from 5.10 before 7.0.

Weakness: CWE-23 (Relative Path Traversal)

## Which versions are affected by CVE-2026-21620?


## How do I fix CVE-2026-21620?

Upgrade to a fixed version.

## Is CVE-2026-21620 being exploited?

There is no known exploitation of CVE-2026-21620 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-21620 and fix it if it is affected.

What it is: CVE-2026-21620 is a low-severity path traversal vulnerability in Erlang OTP, published on 20 Feb 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-21620 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-2026-21620/ (Markdown: https://insights.sbomify.com/CVE-2026-21620/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-21620
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-21620
- OSV: https://osv.dev/vulnerability/CVE-2026-21620

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-21620/
Summaries are generated and may contain mistakes; the official description above is the record.