CVE-2026-53422: SFTP REALPATH path-existence oracle allowing filesystem enumeration…

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.

Timeline

2026
9 Jun 2026
9 Jun 2026
ID reserved
By EEF
2 Jul 202623 days later
2 Jul 2026· 23 days later
Published
24 Jul 202622 days later
24 Jul 2026· 22 days later
Record updated

Changes after publication (a new score, a public exploit, EPSS crossing 1, 10 or 50 %, leaving KEV) are kept since November 2026; earlier ones are not known.

Scores

CVSS scores of CVE-2026-53422, by who scored it
Scored by	CVSS	Score	Vector
EEFCNA (assigner)	4.0	Low2.3	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
NVDNVD · Modified	4.0	Low2.3	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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS (exploitation in 30 days): 0.26% · top 82% of all CVEs (7 Nov 2026)
CISA SSVC: Exploitation: none · Automatable: no · Technical impact: partial

The list uses the assigner's score when there is one, then CISA's, then NVD's: Low 2.3.

Weakness

CWE-204 Observable Response Discrepancy (opens in a new tab)All about CWE-204 and its CVEs

Affected products

Erlang · OTP
- affected 3.0.1 – < *
Erlang · OTP
- affected 17.0 – < *
- affected 84adefa331c4159d432d22840663c38f155cd4c1 – < *

What to do

Workaround: * Use OS-level chroot to run the Erlang VM or SFTP server process in an isolated filesystem environment, eliminating reliance on the application-level root option. * Ensure the SFTP server port on the machine running the Erlang/OTP SFTP server is not reachable from untrusted machines. * Ensure that no sensitive information (usernames, project names, mount topology) is inferrable from the existence or non-existence of paths on the host filesystem.

References (7)

Sources

The same CVE in the primary databases and aggregators, to check against.

Badge for a README or a ticket

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Record last updated 24 Jul 2026, 14:16 UTC.

SFTP REALPATH path-existence oracle allowing filesystem enumeration outside configured root