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.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-21620?
How do I fix CVE-2026-21620?
Upgrade to a fixed version.
Upgrade, and resolve every user-supplied path against an allowed base folder before opening it. More about Path traversal.
Is CVE-2026-21620 being exploited?
There is no known exploitation of CVE-2026-21620 in the wild and no public exploit code.
Sources
Also known as AZL-78278, AZL-78285, DEBIAN-CVE-2026-21620, EEF-CVE-2026-21620, GHSA-hmrc-prh3-rpvp, OESA-2026-2703 and 2 more.