CVE-2026-64667

MEDIUMCVSS 4.4/10

Last modified

CVE-2026-64667 is a medium-severity vulnerability rated 4.4/10 on the CVSS scale. 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.

Description

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.

Metrics

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
mcdopepam_usb< 0.9.3

References

Timeline

Published
Last Modified
Status
Received

Frequently Asked Questions

What is CVE-2026-64667?
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.
How severe is CVE-2026-64667?
CVE-2026-64667 has a CVSS score of 4.4/10 (MEDIUM severity).
How do I fix CVE-2026-64667?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST