What is CVE-2025-71263?

CVE-2025-71263 is a high-severity vulnerability in At&t Bell Labs Unix, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 7.4/10. Published 2026-03-13.

How severe is CVE-2025-71263?

High severity. CVSS v3 base score is 7.4 out of 10.

Buffer overflow in At&t Bell Labs Unix

CVE-2025-71263

In UNIX Fourth Research Edition (v4), the su command is vulnerable to a buffer overflow due to the 'password' variable having a fixed size of 100 bytes. A local user can exploit this to gain root privileges. It is unlikely that UNIX v4 is…

Vulnerability class: Buffer Overflow

EPSS: 0.000 (0.4th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 7.4 (High). Vector: CVSS:3.1/AV:L/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.

Affected products

At&t Bell Labs Unix — versions 4

Weakness classification (CWE)

CWE-120 — Buffer Copy without Checking Size of Input (Classic Buffer Overflow)

References

Frequently asked questions

What is CVE-2025-71263?: CVE-2025-71263 is a high-severity vulnerability in At&t Bell Labs Unix, classified under Buffer Copy without Checking Size of Input (Classic Buffer Overflow). CVSS score: 7.4/10. Published 2026-03-13.
How severe is CVE-2025-71263?: High severity. CVSS v3 base score is 7.4 out of 10.