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CVE-2026-48859 Erlang CVE debrief

CVE-2026-48859 is a medium-severity vulnerability in Erlang/OTP SSH. The vulnerability, known as an Observable Timing Discrepancy, allows an unauthenticated remote attacker to enumerate valid usernames via a timing side-channel in password authentication. The issue arises when the SSH daemon is configured with the user_passwords or password option, causing ssh_auth:check_password/3 to perform a PBKDF2-SHA256 computation with 600,000 iterations for valid usernames, but return immediately for invalid usernames. This timing difference is detectable in a single authentication attempt.

Vendor
Erlang
Product
OTP
CVSS
MEDIUM 6.3
CISA KEV
Not listed in stored evidence
Original CVE published
2026-06-10
Original CVE updated
2026-09-08
Advisory published
2026-06-10
Advisory updated
2026-09-08

Who should care

Users of Erlang/OTP SSH, particularly those who have configured the SSH daemon with the user_passwords or password option, should be aware of this vulnerability. The recommended alternative, pwdfun, is not affected.

Technical summary

The vulnerability is associated with program files lib/ssh/src/ssh_auth.erl and lib/ssh/src/ssh_options.erl. It affects OTP from OTP 29.0 before 29.0.2, corresponding to ssh from 6.0 before 6.0.1.

Defensive priority

medium

Recommended defensive actions

  • Update to OTP 29.0.2 or later, or ssh 6.0.1 or later.
  • Consider using the pwdfun option instead of user_passwords or password.

Evidence notes

The CVE record and details are sourced from official databases and vendor advisories.

Sources and references

Verified primary and authoritative sources

  • CVE-2026-48859 CVE Program record

    Publisher, destination, and source semantics verified

    URL: https://www.cve.org/CVERecord?id=CVE-2026-48859

    CVE Program - Official CVE Program record with source-provided CVE metadata.

  • CVE-2026-48859 NVD vulnerability detail

    Publisher, destination, and source semantics verified

    URL: https://nvd.nist.gov/vuln/detail/CVE-2026-48859

    NIST National Vulnerability Database - Official NIST NVD detail page and source-specific vulnerability assessment.

Supplemental references

  • Source reference

    Unverified legacy reference

    URL: https://cna.erlef.org/cves/CVE-2026-48859.html

    6b3ad84c-e1a6-4bf7-a703-f496b71e49db

  • Source reference

    Unverified legacy reference

    URL: https://github.com/erlang/otp/commit/c342092ef4b369bb409d5b71ac8fd83bab74aedf

    6b3ad84c-e1a6-4bf7-a703-f496b71e49db

  • Source reference

    Unverified legacy reference

    URL: https://github.com/erlang/otp/security/advisories/GHSA-3w6p-vwhf-wvp4

    6b3ad84c-e1a6-4bf7-a703-f496b71e49db

  • Source reference

    Unverified legacy reference

    URL: https://osv.dev/vulnerability/EEF-CVE-2026-48859

    6b3ad84c-e1a6-4bf7-a703-f496b71e49db

  • Source reference

    Unverified legacy reference

    URL: https://www.erlang.org/doc/system/versions.html

    6b3ad84c-e1a6-4bf7-a703-f496b71e49db

Methodology and review provenance

AI-assisted synthesis based on stored public vulnerability evidence. System validation, approval state, and publication status do not by themselves establish human review of this revision. PatchSiren helps prioritize defensive review and does not prove exposure or remediation on any system.