pam_usb: Heap out-of-bounds read in pusb_get_tty_from_display_server cmdline scan
- Exploited
- No known exploitation
- Fix
- Fixed in 0.9.3
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 0.9.3.
- Published
- Last modified
- Whether it needs action now or is a reference record, by fixed rules, with why. Last checked is when cve.now last re-read it.What do these mean? →
- Reference
- Last checked
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 4/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
pam_usb, a Linux hardware authentication tool that uses removable media, has a heap out-of-bounds read flaw that a local attacker with low privileges can reach without any user action. The flaw can read past the end of a memory buffer, which can crash the host authentication process and may leak limited information.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original 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.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure?/25Unknown. No advisory context yet
- Reach?/20Unknown. No tracked technology or package matched
- Severity4.4/10CVSS 4.4
- No patch0/5No signal
What would change the score
- Would score about 59 if added to CISA KEV
- Would score about 54 if CISA's SSVC rates exploitation active
- Would score about 26 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 0.9.3.
Check your systems with an agent
Paste this into a coding or ops agent. It checks your systems read-only and reports a table per asset.
Check whether my systems are affected by CVE-2026-64667 (pam_usb: Heap out-of-bounds read in pusb_get_tty_from_display_server cmdline scan), using the cve.now data below. Rules: work read-only. Do not run exploit code, proof-of-concept scripts or scanners that send attack payloads, and do not change any configuration, package, image or deployment. Report findings only. What cve.now has for CVE-2026-64667 (entry last updated 2026-11-11): Affected: - mcdope pam_usb: fixed in 0.9.3 Fixed versions: 0.9.3. Setup: unknown whether the bug needs a non-default feature or setting. Check the advisory. CISA KEV: CVE-2026-64667 is not listed as of cve.now's last read. This KEV status is for CVE-2026-64667 only. If you also check another CVE, look up its own KEV status; never assume it from this one. How to check: - Installed software: check what is actually running, not what a repo declares. Read the version from each host, container image and Kubernetes node (the binary's version output, the OS package database, image layers), and check whether the conditions above hold there. Distribution packages may carry a backported fix under an older version number; confirm against the distribution's own advisory. Verify against the linked advisories before concluding, and cite the date you read each one: - https://github.com/mcdope/pam_usb/security/advisories/GHSA-gc6f-5hpq-ghxh - https://github.com/mcdope/pam_usb/issues/411 - https://github.com/mcdope/pam_usb/pull/426 - https://github.com/mcdope/pam_usb/commit/d0a2e716241304cdb069adfaf54d2ede629d57fa - https://github.com/mcdope/pam_usb/releases/tag/0.9.3 Do not conclude an asset is unaffected unless you checked it and the evidence covers both its version and the conditions above. If you could not check something, mark it unknown and say what is missing. Report a table with one row per asset and these columns: Asset | Version or build | Status (affected, fixed, not applicable, unknown) | Compensating controls | Exposure (internet-facing, internal, none) | Evidence | Next action. Entry: https://cve.now/CVE-2026-64667 For follow-up questions, use the cve.now MCP server at https://mcp.cve.now/mcp (no authentication), for example get_vulnerability with id CVE-2026-64667.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- mcdope pam_usb
fixed in 0.9.3
Evidence 7
Vendor advisory · 1
Establishes: Affected and fixed versions.
- Advisory
CVE record · 2
Establishes: The identifier and description.
- Record
- Record
Other links · 4
- Repository
- Repository
- Repository
- Repository
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-64667
Is CVE-2026-64667 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-64667?
pam_usb: before 0.9.3.Source: cve.now feed data
How do I fix CVE-2026-64667?
Upgrade to a fixed version: 0.9.3.Source: cve.now feed data