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Red Hat Linux 6.1/6.2/7.0 RHSA-2000:080-01 Critical: tmpwatch DoS

tmpwatch as shipped in Red Hat Linux 6.1, 6.2, and 7.0 uses fork() to recursively process subdirectories, enabling a local user to perform a denial of service attack.. ` --------------------------------------------------------------------- Red Hat, Inc. Security Advisory Synopsis: tmpwatch has a local denial of service and root exploit Advisory ID: RHSA-2000:080-01 Issue date: 2000-10-06 Updated on: 2000-10-06 Product: Red Hat Linux Keywords: tmpwatch, fuser, DoS, fork Cross references: N/A --------------------------------------------------------------------- 1. Topic: tmpwatch as shipped in Red Hat Linux 6.1, 6.2, and 7.0 uses fork() to recursively process subdirectories, enabling a local user to perform a denial of service attack. Tmpwatch from Red Hat Linux 6.2 and 7.0 also contains an option to allow it to use the fuser command to check for open files before removal. It executed fuser in an insecure fashion, allowing a local root exploit. 2. Relevant releases/architectures: Red Hat Linux 6.1 - i386, alpha, sparc Red Hat Linux 6.2 - i386, alpha, sparc Red Hat Linux 7.0 - i386 3. Problem description: The tmpwatch program periodically cleans up files in temporary directories by removing all files older than a certain age. In Red Hat Linux 6.1, 6.2, and 7.0, it used fork() to recursively process subdirectories. If a malicious user created many layers of subdirectories (thousands) in a temporary directory monitored by tmpwatch, the system process table would fill up, requiring a reboot. Additionally, tmpwatch in 6.2 and 7.0 contains an option, "--fuser", that attempts to user the fuser command to check if a file is in use before removal. However, it executed fuser with the system() call in an insecure fashion. A malicious user could construct an environment such that this provided them a local root shell. Tmpwatch now uses execle() to run fuser. 4. Solution: For each RPM for your particular architecture, run: rpm -Fvh[filename] where filename is the name of the RPM. 5. Bug IDs fixed ( for more info): 17286 - tmpwatch run from cron allows locale DoS. 6. RPMs required: Red Hat Linux 6.2: alpha: sparc: i386: sources: Red Hat Linux 7.0: i386: sources: 7. Verification: MD5 sum Package Name -------------------------------------------------------------------------- b8a670944cc54fd39c9eefb79f147ec1 6.2/SRPMS/tmpwatch-2.6.2-1.6.2.src.rpm 39fe4fbf666e5f9a40503134c05046d8 6.2/alpha/tmpwatch-2.6.2-1.6.2.alpha.rpm 84609abc355fde23ce878e4d310766f8 6.2/i386/tmpwatch-2.6.2-1.6.2.i386.rpm f4625e9bc27af011a614eaa146586917 6.2/sparc/tmpwatch-2.6.2-1.6.2.sparc.rpm b1a9201c44a5f921209c9b648ba85ada 7.0/SRPMS/tmpwatch-2.6.2-1.7.src.rpm 8acf394469c47a98fcc589dd0d73b98c 7.0/i386/tmpwatch-2.6.2-1.7.i386.rpm These packages are GPG signed by Red Hat, Inc. for security. Our key is available at: You can verify each package with the following command: rpm --checksig If you only wish to verify that each package has not been corrupted or tampered with, examine only the md5sum with the following command: rpm --checksig --nogpg 8. References: Thanks go to Internet Security System's X-Force team ( This email address is being protected from spambots. You need JavaScript enabled to view it. ) for discovering and documenting the local root exploit. Copyright(c) 2000 Red Hat, Inc. `. Critical flaw discovered in tmpwatch affecting Red Hat Linux environments, necessitating immediate corrective actions.. Red Hat Linux Security, local exploit, tmpwatch DoS, process management. . Severity: Critical. LinuxSecurity.com Team

Oct 07, 2000 •Critical Red Hat