Erlang OTP up to 29.0.1 lib/ssh/src/ssh_auth.erl timing discrepancy

Summaryinfo

A vulnerability, which was classified as problematic, has been found in Erlang OTP up to 29.0.1. This impacts an unknown function in the library lib/ssh/src/ssh_auth.erl. Performing a manipulation results in timing discrepancy. This vulnerability was named CVE-2026-48859. The attack may be initiated remotely. There is no available exploit. It is advisable to upgrade the affected component.

Detailsinfo

A vulnerability was found in Erlang OTP up to 29.0.1. It has been classified as problematic. This affects an unknown functionality in the library lib/ssh/src/ssh_auth.erl. The manipulation with an unknown input leads to a timing discrepancy vulnerability. CWE is classifying the issue as CWE-208. Two separate operations in a product require different amounts of time to complete, in a way that is observable to an actor and reveals security-relevant information about the state of the product, such as whether a particular operation was successful or not. This is going to have an impact on confidentiality. The summary by CVE is:

Observable Timing Discrepancy vulnerability in Erlang/OTP ssh (ssh_auth, ssh_options modules) allows unauthenticated remote username enumeration via timing side-channel in password authentication. When the SSH daemon is configured with the user_passwords or password option, ssh_auth:check_password/3 performs a PBKDF2-SHA256 computation with 600,000 iterations (~300ms) for valid usernames, but returns immediately (~0ms) for invalid usernames via the ssh_options:get_password_option/2 path. This timing difference is detectable in a single authentication attempt and allows an unauthenticated attacker to distinguish valid from invalid usernames. The user_passwords and password options are documented as intended for test purposes; the recommended alternative is pwdfun, which is not affected by this vulnerability. This vulnerability is associated with program files lib/ssh/src/ssh_auth.erl and lib/ssh/src/ssh_options.erl. This issue affects OTP from OTP 29.0 before 29.0.2 corresponding to ssh from 6.0 before 6.0.1.

The weakness was presented by Zhang Delong as GHSA-3w6p-vwhf-wvp4. It is possible to read the advisory at github.com. This vulnerability is uniquely identified as CVE-2026-48859 since 05/25/2026. The exploitability is told to be difficult. It is possible to initiate the attack remotely. No form of authentication is needed for exploitation. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1592 according to MITRE ATT&CK.

Upgrading to version 29.0.2 eliminates this vulnerability. Applying the patch c342092ef4b369bb409d5b71ac8fd83bab74aedf is able to eliminate this problem. The bugfix is ready for download at github.com. The best possible mitigation is suggested to be upgrading to the latest version.

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Productinfo

Vendor

• Erlang

Name

• OTP

Version

• 29.0.0
• 29.0.1

License

• open-source

Website

• Product: https://github.com/erlang/otp/

CPE 2.3info

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CPE 2.2info

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