CVE-2026-47269 (GCVE-0-2026-47269)

Vulnerability from cvelistv5 – Published: 2026-05-27 20:11 – Updated: 2026-05-28 12:50
VLAI
Title
pam_usb: deny_remote feature incorrectly classifies IPv4-mapped IPv6 remote connections as local
Summary
pam_usb provides hardware authentication for Linux using ordinary removable media. Prior to 0.9.0, pam_usb's deny_remote feature checks utmpx ut_addr_v6 to detect whether an authentication request originates from a remote session. The outer guard was if (utent->ut_addr_v6[0] != 0), which only tests the first 32-bit word of the 128-bit address field. IPv4-mapped IPv6 addresses (::ffff:x.x.x.x) store the IPv4 address in ut_addr_v6[3] with ut_addr_v6[0] == 0. On systems where the SSH daemon listens on :: (IPv6 wildcard) with AddressFamily any -- common on Ubuntu and Debian -- incoming IPv4 connections are recorded in utmpx as IPv4-mapped IPv6 addresses. The outer check evaluates to false, the remote-detection block is skipped entirely, and the session is treated as local. deny_remote=true does not block the authentication. An attacker with physical access to a registered USB device can authenticate over SSH on an affected system as if they were sitting at a local terminal, bypassing the deny_remote restriction. This vulnerability is fixed in 0.9.0.
Severity
7.4 (High)
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:N
SSVC
Exploitation: none Automatable: no Technical Impact: total
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-05-28 12:50 UTC
CWE
  • CWE-284 - Improper Access Control
Assigner
References
Impacted products
Vendor Product Version
mcdope pam_usb Affected: < 0.9.0
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Sightings

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Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
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