CVE-2026-48855

Ein Angreifer kann mehrere Schwachstellen in Erlang/OTP ausnutzen, um Sicherheitsvorkehrungen zu umgehen, Daten zu manipulieren, vertrauliche Informationen offenzulegen oder einen Denial-of-Service-Zustand zu verursachen.

## Summary Exposure of Sensitive Information to an Unauthorized Actor vulnerability in Erlang OTP ssh (`ssh_sftpd` module) allows File Discovery. The `SSH_FXP_READLINK` handler in `ssh_sftpd` sends the raw result of `file:read_link/2` to the client without calling `chroot_filename/2` to strip the backend root prefix. An authenticated SFTP client can create a symlink inside the chroot pointing to `/`; `ssh_sftpd` resolves the target to the absolute backend root and stores it on disk. Reading the symlink back via `SSH_FXP_READLINK` returns that absolute path, for example `/data/sftp`, instead of the chrooted value `/`. The information disclosed is the absolute filesystem path of the SFTP root directory and of any symlink targets within it. No file contents, credentials, or access to paths outside the root directory are obtainable through this issue alone. This vulnerability is associated with program files `lib/ssh/src/ssh_sftpd.erl`. This issue affects OTP from OTP 17.0 before OTP 27.3.4.13, OTP 28.5.0.2, and OTP 29.0.2, corresponding to ssh from 3.0.1 before 5.2.11.8, 5.5.2.1, and 6.0.1. Whether OTP before OTP 17.0, corresponding to ssh before 3.0.1, is affected is unknown. ## Workarounds * Use OS-level chroot to run the Erlang VM/SFTP server process in an isolated filesystem environment, eliminating reliance on the application-level `root` option. * Ensure that the SFTP server port is not reachable from untrusted machines. * Ensure that no sensitive information (usernames, project names, mount topology) is inferrable from the absolute path of the configured root directory. ## Configurations The SFTP subsystem must be enabled on the SSH server and the `root` option must be configured in the `ssh_sftpd:subsystem_spec/1` call. Deployments without the `root` option are not affected.