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CVE-2026-39461— select(2) file descriptor set overflow causes stack overflow

Quick assessment

Affected
FreeBSD FreeBSD
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.

FreeBSD是FreeBSD基金会的一套类Unix操作系统。 FreeBSD存在安全漏洞，该漏洞源于未验证套接字描述符是否在FD_SETSIZE限制内，可能导致栈损坏。如果目标应用程序以setuid root权限运行，可能用于提升本地权限。

AI Predicted 7.8 Difficulty: Moderate EPSS 0.17% · P7

Possible ATT&CK Techniques 1 AI

T1068 · Exploitation for Privilege Escalation

Affected Version Matrix 3

VendorProduct Version RangeStatus
FreeBSD FreeBSD 15.0-RELEASE< p9 affected
14.4-RELEASE< p5 affected
14.3-RELEASE< p14 affected
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I. Basic Information for CVE-2026-39461

Vulnerability Information
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Vulnerability Title
select(2) file descriptor set overflow causes stack overflow
Source: CVE Program / CVE List V5
Vulnerability Description
libcasper(3) communicates with helper processes via UNIX domain sockets, and uses the select(2) system call to wait for data to become available. However, it does not verify that its socket descriptor fits within select(2)'s descriptor set size limit of FD_SETSIZE (1024). An attacker able to cause an application using libcasper(3) to allocate large file descriptors, e.g., by opening many descriptors and executing a program which is not careful to close them upon startup, may trigger stack corruption. If the target application runs with setuid root privileges, this could be used to escalate local privileges.
Source: CVE Program / CVE List V5
CVSS Information
N/A
Source: CVE Program / CVE List V5
Vulnerability Type
栈缓冲区溢出
Source: CVE Program / CVE List V5
Vulnerability Title
FreeBSD 安全漏洞
Source: CNNVD (China National Vulnerability Database)
Vulnerability Description
FreeBSD是FreeBSD基金会的一套类Unix操作系统。 FreeBSD存在安全漏洞，该漏洞源于未验证套接字描述符是否在FD_SETSIZE限制内，可能导致栈损坏。如果目标应用程序以setuid root权限运行，可能用于提升本地权限。
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
FreeBSD FreeBSD 15.0-RELEASE ~ p9 -

II. Public POCs for CVE-2026-39461

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III. Intelligence Information for CVE-2026-39461

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Vendor Advisories for CVE-2026-39461 (1)

Same Patch Batch · FreeBSD · 2026-05-21 · 7 CVEs total

CVE-2026-45250 Stack buffer overflow via setcred(2)
CVE-2026-45252 Heap overflow in FUSE_LISTXATTR
CVE-2026-45255 Remote code execution via installer Wi-Fi access point scans
CVE-2026-45251 Kernel use-after-free via file descriptor syscalls
CVE-2026-45253 Missing validation in ptrace(PT_SC_REMOTE)
CVE-2026-45254 Incorrect libcap_net limitation list manipulation

IV. Related Vulnerabilities

Same product: FreeBSD
Same vendor: FreeBSD
Same weakness: CWE-121

V. Comments for CVE-2026-39461

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