CVE-2026-53422

Publication date 2 July 2026

Last updated 8 October 2026

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

4.3 · Medium

Score breakdown

Description

Observable Response Discrepancy vulnerability in Erlang OTP ssh (ssh_sftpd module) allows an authenticated SFTP user to enumerate the existence of files and directories outside the configured root directory. The SSH_FXP_REALPATH handler in ssh_sftpd calls relate_file_name/3 with Canonicalize=false, unlike every other SFTP operation handler. This allows .. components in the requested path to bypass the is_within_root/2 check without being resolved. The un-canonicalized path then enters resolve_symlinks/2, which walks up the directory tree above the configured root and issues read_link() syscalls on arbitrary filesystem paths. An authenticated SFTP client can exploit this by sending a REALPATH request with a crafted traversal path. The server response differs depending on whether the target path exists on the host filesystem (SSH_FXP_NAME when the path resolves successfully, SSH_FX_NO_SUCH_FILE when it does not). This creates a path-existence oracle that an attacker can use to enumerate the filesystem structure outside the configured root, including the existence of sensitive files, directories, and mount points. The vulnerability leaks only the existence of paths. No file contents, credentials, or write access are obtainable through this issue alone. The information gained may assist further attacks when combined with other vulnerabilities. This vulnerability is associated with program files lib/ssh/src/ssh_sftpd.erl and program routine ssh_sftpd:handle_op/4. This issue affects OTP from OTP 17.0 before OTP 29.0.3, OTP 28.5.0.3 and OTP 27.3.4.14, corresponding to ssh from 3.0.1 before 6.0.2, 5.5.2.2 and 5.2.11.9.

Status

Package Ubuntu Release Status
erlang 26.04 LTS resolute
Fixed 1:27.3.4.6+dfsg-1ubuntu0.2
25.10 questing Ignored end of life, was needs-triage
24.04 LTS noble
Fixed 1:25.3.2.8+dfsg-1ubuntu4.8
22.04 LTS jammy
Fixed 1:24.2.1+dfsg-1ubuntu0.8
20.04 LTS focal
Fixed 1:22.2.7+dfsg-1ubuntu0.5+esm3
18.04 LTS bionic
Fixed 1:20.2.2+dfsg-1ubuntu2+esm4
16.04 LTS xenial
Fixed 1:18.3-dfsg-1ubuntu3.1+esm4
14.04 LTS trusty
Fixed 1:16.b.3-dfsg-1ubuntu2.2+esm3

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Severity score breakdown

CVSS version:

Base score 2.3 · Low

Vector: CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N

Base score 4.3 · Medium

Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N

References

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