RHSA-2002:132

Vulnerability from csaf_redhat - Published: 2002-07-29 15:00 - Updated: 2025-11-21 17:24
Summary
Red Hat Security Advisory: : : : Updated util-linux package fixes password locking race
Severity
Moderate
Notes
Topic: A locally exploitable vulnerability is present in the util-linux package which shipped with Red Hat Linux. [Updated 8 July 2003] Added packages for Red Hat Linux on IBM iSeries and pSeries systems.
Details: The util-linux package contains a large variety of low-level system utilities that are necessary for a Linux system to function. The chfn utility included in this package allows users to modify personal information stored in the system-wide password file, /etc/passwd. In order to modify this file, this application is installed setuid root. Under certain conditions, a carefully crafted attack sequence can be performed to exploit a complex file locking and modification race present in this utility allowing changes to be made to /etc/passwd. In order to successfully exploit the vulnerability and perform privilege escalation there is a need for minimal administrator interaction. Additionally, the password file must be over 4 kilobytes, and the local attackers entry must not be in the last 4 kilobytes of the password file. The Common Vulnerabilities and Exposures project (cve.mitre.org) has assigned the name CAN-2002-0638 to this issue. An interim workaround is to remove setuid flags from /usr/bin/chfn and /usr/bin/chsh. All users of Red Hat Linux should update the packages contained in this erratum, which are patched to correct this vulnerability. Many thanks to Michal Zalewski of Bindview for alerting us to this issue.
Terms of Use: This content is licensed under the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/). If you distribute this content, or a modified version of it, you must provide attribution to Red Hat Inc. and provide a link to the original.
CVE-2002-0638

setpwnam.c in the util-linux package, as included in Red Hat Linux 7.3 and earlier, and other operating systems, does not properly lock a temporary file when modifying /etc/passwd, which may allow local users to gain privileges via a complex race condition that uses an open file descriptor in utility programs such as chfn and chsh.

Affected products
Product Identifier Version Remediation
Red Hat Linux 6.2
Red Hat / Red Hat Linux
 cpe:/o:redhat:linux:6.2 —
Vendor Fix fix
Red Hat Linux 7.0
Red Hat / Red Hat Linux
 cpe:/o:redhat:linux:7.0 —
Vendor Fix fix
Red Hat Linux 7.1
Red Hat / Red Hat Linux
 cpe:/o:redhat:linux:7.1 —
Vendor Fix fix
Red Hat Linux 7.2
Red Hat / Red Hat Linux
 cpe:/o:redhat:linux:7.2 —
Vendor Fix fix
Red Hat Linux 7.3
Red Hat / Red Hat Linux
 cpe:/o:redhat:linux:7.3 —
Vendor Fix fix
Threats
Impact Moderate
References
To clipboard 

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        "text": "The util-linux package contains a large variety of low-level system\nutilities that are necessary for a Linux system to function. The chfn\nutility included in this package allows users to modify personal\ninformation stored in the system-wide password file, /etc/passwd. In order\nto modify this file, this application is installed setuid root.\n\nUnder certain conditions, a carefully crafted attack sequence can be\nperformed to exploit a complex file locking and modification race present\nin this utility allowing changes to be made to /etc/passwd.  \n\nIn order to successfully exploit the vulnerability and perform privilege\nescalation there is a need for minimal administrator interaction. \nAdditionally, the password file must be over 4 kilobytes, and the local\nattackers entry must not be in the last 4 kilobytes of the password file.\n\nThe Common Vulnerabilities and Exposures project (cve.mitre.org) has\nassigned the name CAN-2002-0638 to this issue.\n\nAn interim workaround is to remove setuid flags from /usr/bin/chfn and\n/usr/bin/chsh.  All users of Red Hat Linux should update the packages\ncontained in this erratum, which are patched to correct this vulnerability.\n\nMany thanks to Michal Zalewski of Bindview for alerting us to this issue.",
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