---
title: "CVE-2026-48859\n    | Ubuntu"
description: Ubuntu is an open source software operating system that runs from the
  desktop, to the cloud, to all your internet connected things.
url: https://ubuntu.com/security/CVE-2026-48859?format=md
keywords: index, follow
---

# CVE-2026-48859

Publication date 10 June 2026

Last updated 7 August 2026

---

Ubuntu priority

**Medium**

[Why this priority?](https://ubuntu.com/security/cves/about#priority )

## Cvss 3 Severity Score

**5.3 · Medium**

[Score breakdown](https://ubuntu.com/security/CVE-2026-48859?format=md#impact-score)

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## Description

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 OTP 29.0.2, corresponding to
ssh from 6.0 before 6.0.1.

## Status

Show unmaintained releases

| Package | Ubuntu Release | Status |
| --- | --- | --- |
| erlang | 26.04 LTS resolute | Needs evaluation |
| 25.10 questing | Ignored end of life, was needs-triage |
| 24.04 LTS noble | Needs evaluation |
| 22.04 LTS jammy | Needs evaluation |
| 20.04 LTS focal | Needs evaluation |
| 18.04 LTS bionic | Needs evaluation |
| 16.04 LTS xenial | Needs evaluation |
| 14.04 LTS trusty | Needs evaluation |

---

* [How can I get the fixes?](https://ubuntu.com/security/cves/about#security)
* [What do statuses mean?](https://ubuntu.com/security/cves/about#statuses)

## Severity score breakdown

CVSS version:

CVSS v4.0

[CVSS v4.0](https://ubuntu.com/security/CVE-2026-48859?format=md)
[CVSS v3.0](https://ubuntu.com/security/CVE-2026-48859?format=md)

**Base score**

6.3 · Medium

* Base metrics

  | Parameter | Value |
  | --- | --- |
  | Attack vector | Network |
  | Attack complexity | Low |
  | Attack requirements | Present |
  | Privileges required | None |
  | User interaction | None |
  | Vulnerable system - Confidentiality impact | Low |
  | Vulnerable system - Integrity impact | None |
  | Vulnerable system - Availability impact | None |
  | Subsequent system - Confidentiality impact | None |
  | Subsequent system - Integrity impact | None |
  | Subsequent system - Availability impact | None |
* Scores

  | Parameter | Value |
  | --- | --- |
  | Base score | 6.3 · Medium |
  | Base + Threat score | - |
  | Base + Environmental score | - |
  | Base + Threat + Environmental score | - |

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

## References

* [MITRE](https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2026-48859)
* [NVD](https://nvd.nist.gov/vuln/detail/CVE-2026-48859)
* [Launchpad](https://launchpad.net/bugs/cve/CVE-2026-48859)
* [Debian](https://security-tracker.debian.org/tracker/CVE-2026-48859)

### Other references

* <https://www.cve.org/CVERecord?id=CVE-2026-48859>
* <https://cna.erlef.org/cves/CVE-2026-48859.html>
* <https://osv.dev/vulnerability/EEF-CVE-2026-48859>