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Heap-based Buffer OverflowWeakness · CWE-122

CVE-2026-48065

MEDIUM · 6.7 CVSS v3.1 Published 2026-05-27
Mitigation only
No fix yet — a mitigation exists. There is no fixed release. A documented workaround reduces exposure in the meantime.
See remediation →
69/100
Remediation priority · Elevated
Zero-click

Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.

NVD · unedited
pam_usb provides hardware authentication for Linux using ordinary removable media. Prior to 0.9.1, src/conf.c allocates heap memory proportional to n_devices, a count derived from libxml2 XPath evaluation of the config file, without first enforcing an upper bound. On 32-bit targets (armv7l, i686 -- both listed in the project Makefile), the multiplication n_devices * sizeof(t_pusb_device) wraps around size_t, causing xmalloc() to receive a very small size. Because xmalloc() only calls abort() on NULL return, a small-but-non-NULL allocation is accepted, and subsequent array writes overflow the heap. This vulnerability is fixed in 0.9.1.

Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.

dbcve analysis · high confidence

pam_usb versions before 0.9.1 have an integer overflow in src/conf.c where n_devices from XML config is multiplied by sizeof(t_pusb_device) without bounds checking. On 32-bit systems (armv7l, i686), this multiplication wraps around size_t, causing xmalloc() to allocate a much smaller buffer than intended. The subsequent array writes then overflow the heap.

MitigationUpgrade pam_usb to version 0.9.1 or later, which enforces an upper bound on n_devices before allocation. Prior to upgrading, restrict pam_usb deployment to 64-bit systems if possible.

Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.

CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.

From the vector
Attack vector
Local
Complexity
Low
Privileges
High
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:L/AC:L/PR:H/UI:N/S:U/C:H/I:H/A:H

Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.

dbcve checks

Work through these to decide whether this CVE applies to you.

  1. Identify if pam_usb is installed
    Run 'dpkg -l pam-usb' or 'rpm -q pam-usb' or check for /lib/security/pam_usb.so or /lib64/security/pam_usb.so
    Affected if pam_usb package or binary is present on the system
  2. Determine installed pam_usb version
    Run 'dpkg -l pam-usb | grep pam-usb' or 'rpm -q --info pam-usb' or check /usr/share/doc/pam-usb/ for version file
    Affected if Version is below 0.9.1 (e.g., 0.9.0, 0.8.x, etc.)
  3. Identify system architecture
    Run 'uname -m' or 'arch' command
    Affected if Output shows 32-bit architecture such as i686, i386, or armv7l (64-bit systems like x86_64 or aarch64 are not affected by this overflow)
  4. Locate pam_usb XML configuration file
    Check /etc/pam_usb.conf or /etc/pam_usb/*.xml, or search for XML files referenced in pam_usb documentation
    Affected if An XML configuration file exists and contains <device> entries defining multiple authentication devices (the n_devices value read from this file triggers the overflow)
  5. Verify pam_usb module is loaded or configured for authentication
    Check PAM configuration files in /etc/pam.d/ for 'pam_usb.so' entries (e.g., grep -r pam_usb /etc/pam.d/)
    Affected if pam_usb is configured as an authentication module in any PAM service file

A system is affected if pam_usb version is below 0.9.1 AND the system is 32-bit (i686/armv7l) AND pam_usb is configured with an XML config file containing device entries.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.

dbcve · scoped
Mitigation available No clean upgrade yet — mitigate in the meantime
Mitigation

Upgrade pam_usb to version 0.9.1 or later, which enforces an upper bound on n_devices before allocation. Prior to upgrading, restrict pam_usb deployment to 64-bit systems if possible.

Recommended fix High confidence

0.9.1

  1. 1. Identify the current installed version of pam_usb by checking the package manager or running `dpkg -l | grep pam-usb` or `rpm -qa | grep pam-usb`
  2. 2. Download pam_usb version 0.9.1 from the official GitHub repository (github.com/pam-usb) or from your distribution's package repository
  3. 3. If building from source: clone the repository, checkout tag v0.9.1, then run `./configure`, `make`, and `make install` as root
  4. 4. If using a package manager: run `apt-get install pam-usb` (Debian/Ubuntu) or `yum install pam-usb` (RHEL/CentOS) to install the updated package
  5. 5. Verify the installation was successful by checking the version: `pamusb-config --version` or checking the binary
  6. 6. Review the configuration file /etc/pamusb.conf to ensure settings are intact after upgrade
  7. 7. Test the authentication functionality to confirm pam_usb is working correctly

Generated from the published advisory — verify against the referenced sources before acting.

Have this fixed Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing3.0 h
  • Review / QA1.0 h
8.0 hours of engineering $1,390
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2026-48065 in production — separate from our analysis above.

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What this is

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