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CVE-2026-48986— pam_usb: Infinite loop DoS in process-tree walk when parent process exits during authentication

Quick assessment

Affected
mcdope pam_usb
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

mcdope pam_usb是mcdope的认证模块。 mcdope pam_usb 0.9.1及之前版本存在资源管理错误漏洞，该漏洞源于usb_get_process_parent_id()在失败时未初始化*ppid，且pusb_local_login()中同一变量在进程树while循环中被重复使用作为输入和输出，若无法读取/proc/<pid>/stat则PID不更新且循环不终止，可能导致无限循环拒绝服务攻击。

CVSS 4.7 · Medium EPSS 0.14% · P3

Possible ATT&CK Techniques 1 AI

T1499 · Endpoint Denial of Service

Affected Version Matrix 1

VendorProduct Version RangeStatus
mcdope pam_usb < 0.9.2 affected
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I. Basic Information for CVE-2026-48986

Vulnerability Information
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Vulnerability Title
pam_usb: Infinite loop DoS in process-tree walk when parent process exits during authentication
Source: CVE Program / CVE List V5
Vulnerability Description
pam_usb provides hardware authentication for Linux using removable media. In pam_usb 0.9.1 and earlier, usb_get_process_parent_id() can cause an infinite loop DoS because it does not initialize *ppid on failure. In pusb_local_login(), the same variable is reused as input and output in a process-tree while loop; if /proc/<pid>/stat cannot be read (for example, when an ancestor process exits during authentication), the PID is not updated and the loop does not terminate. This hangs the authenticating process (such as sudo, sshd, or login) until it is forcibly terminated. This issue has been fixed in version 0.9.2.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:N/I:N/A:H
Source: CVE Program / CVE List V5
Vulnerability Type
不可达退出条件的循环(无限循环)
Source: CVE Program / CVE List V5
Vulnerability Title
mcdope pam_usb 资源管理错误漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
mcdope pam_usb是mcdope的认证模块。 mcdope pam_usb 0.9.1及之前版本存在资源管理错误漏洞，该漏洞源于usb_get_process_parent_id()在失败时未初始化*ppid，且pusb_local_login()中同一变量在进程树while循环中被重复使用作为输入和输出，若无法读取/proc/<pid>/stat则PID不更新且循环不终止，可能导致无限循环拒绝服务攻击。
Source: CNNVD (China National Vulnerability Database)
CVSS Information
N/A
Source: CNNVD (China National Vulnerability Database)
Vulnerability Type
N/A
Source: CNNVD (China National Vulnerability Database)

Affected Products

Vendor Product Affected Versions CPE Subscribe
mcdope pam_usb < 0.9.2 -

II. Public POCs for CVE-2026-48986

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III. Intelligence Information for CVE-2026-48986

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Patches & Fixes for CVE-2026-48986 (1)

Vendor Advisories for CVE-2026-48986 (1)

Same Patch Batch · mcdope · 2026-06-18 · 7 CVEs total

CVE-2026-48981 6.7 MEDIUM pam_usb: xmlReadFile flags=0 permits XXE network entity fetching in conf.c
CVE-2026-48980 6.3 MEDIUM pam_usb: getenv() used in PAM context allows environment variable injection into local-che
CVE-2026-48982 5.8 MEDIUM pam_usb: Missing O_EXCL on pad temp file creation allows concurrent update race
CVE-2026-48983 5.8 MEDIUM pam_usb: TOCTOU race condition in pad directory creation allows symlink substitution
CVE-2026-48985 5.5 MEDIUM pam_usb: NULL Dereference Crash in pusb_is_loginctl_local when loginctl Returns Empty Remo
CVE-2026-48984 4.7 MEDIUM pam_usb: xfree() does not call explicit_bzero — sensitive cryptographic material may linge

IV. Related Vulnerabilities

Same product: pam_usb
Same vendor: mcdope
Same weakness: CWE-835

V. Comments for CVE-2026-48986

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