pam_usb: PINENTRY_FALLBACK_APP environment variable allows arbitrary command execution

pam_usb provides hardware authentication for Linux using ordinary removable media. Prior to 0.8.7, pamusb-pinentry reads the PINENTRY_FALLBACK_APP environment variable and executes it directly without any validation. Any process that can set environment variables before pamusb-pinentry is invoked can point PINENTRY_FALLBACK_APP at an arbitrary binary or script and have it executed with the privileges of the pam_usb tool chain. This vulnerability is fixed in 0.8.7.

Problem type

CWE-78: Improper Neutralization of Special Elements used in an OS Command ('OS Command Injection')

Affected products

mcdope

pam_usb

< 0.8.7 - AFFECTED

References

https://github.com/mcdope/pam_usb/security/advisories/GHSA-jxrj-q67x-wr4c

https://github.com/mcdope/pam_usb/security/advisories/GHSA-jxrj-q67x-wr4c

x_refsource_CONFIRM

JSON source

https://cveawg.mitre.org/api/cve/CVE-2026-44709

Click to expand

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    "dateUpdated": "2026-05-27T20:20:52.529Z",
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        "shortName": "GitHub_M",
        "dateUpdated": "2026-05-27T20:20:52.529Z"
      },
      "title": "pam_usb: PINENTRY_FALLBACK_APP environment variable allows arbitrary command execution",
      "descriptions": [
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          "value": "pam_usb provides hardware authentication for Linux using ordinary removable media. Prior to 0.8.7, pamusb-pinentry reads the PINENTRY_FALLBACK_APP environment variable and executes it directly without any validation. Any process that can set environment variables before pamusb-pinentry is invoked can point PINENTRY_FALLBACK_APP at an arbitrary binary or script and have it executed with the privileges of the pam_usb tool chain. This vulnerability is fixed in 0.8.7."
        }
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      "affected": [
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              "type": "CWE"
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            "attackComplexity": "LOW",
            "privilegesRequired": "LOW",
            "userInteraction": "NONE",
            "scope": "UNCHANGED",
            "confidentialityImpact": "HIGH",
            "integrityImpact": "HIGH",
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