# CVE-2026-64667: pam_usb: Heap out-of-bounds read in pusb_get_tty_from_display_server cmdline scan

Status: published. Published: 2026-11-11. Updated: 2026-11-11.

pam_usb provides hardware authentication for Linux using removable media. Prior to version 0.9.3, src/local.c (pusb_get_tty_from_display_server) allocates a 4096-byte cmdline buffer, reads up to 4096 bytes from /proc//cmdline, then replaces every NUL separator with a space. When read(2) returns exactly 4096 bytes for any process the function inspects, the buffer ends without a terminator and the subsequent strstr() calls scan past the allocation boundary. The function is invoked during normal PAM authentication when DISPLAY is set, so the read fires for every process at auth time. Consequences are bounded: strstr output is a Boolean substring match (limited info-disclosure surface) but a hostile heap layout can produce a SIGSEGV that terminates the host PAM process. This issue has been patched in version 0.9.3.

## Remediation

No remediation reported in collected sources

## Affected products and versions

- mcdope / pam_usb: < 0.9.3 (affected). Source: CNA: GitHub_M

## Severity and prioritization

- CVSS 3.1: 4.4 (medium); CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:L; source: CNA: GitHub_M

- CISA KEV: No listing in collected sources

- EPSS: Not available

- SSVC: Not available

- Weaknesses: CWE-125

## Exploit evidence

No exploit evidence in collected sources. This is not proof of no exploitation.

## References

- https://github.com/mcdope/pam_usb/security/advisories/GHSA-gc6f-5hpq-ghxh (CNA: GitHub_M; x_refsource_CONFIRM)

- https://github.com/mcdope/pam_usb/issues/411 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/mcdope/pam_usb/pull/426 (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/mcdope/pam_usb/commit/d0a2e716241304cdb069adfaf54d2ede629d57fa (CNA: GitHub_M; x_refsource_MISC)

- https://github.com/mcdope/pam_usb/releases/tag/0.9.3 (CNA: GitHub_M; x_refsource_MISC)

## Provenance

- CNA: GitHub_M: https://www.cve.org/CVERecord?id=CVE-2026-64667; retrieved 2026-11-11; source updated 2026-11-11

Revision: feb92e54cc9f96dd5e6663b4a42dc22b4c23a46e0b282eaf517e23bbd423ca10

Canonical: https://y2.dev/cve/CVE-2026-64667

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