Copyright © 2012 Red Hat, Inc. All rights reserved. Moderate 2026-07-24T07:44:54 coreutils: GNU coreutils unexpand: Denial of Service via crafted tab stop values 4.4 CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:L CWE-787

GNU coreutils unexpand is vulnerable to a heap-based buffer overflow due to an integer overflow during buffer allocation when processing large tab stop (-t) values. The multiplication used to calculate the allocation size can wrap around, resulting in an undersized buffer. When processing crafted input, subsequent writes exceed the allocated memory, leading to an out‑of‑bounds heap write. When running GNU coreutils unexpand with attacker-provided large tab stop (-t) arguments, this behavior leads to a crash and potentially achieve a heap write primitive depending on memory layout. This issue has been fixed in the commit b60a159fdc5bfcf9988d3a4cb6f53abe8ad5d35d

A flaw was found in GNU coreutils, specifically in the `unexpand` utility. This vulnerability, a heap-based buffer overflow, occurs due to an integer overflow when `unexpand` processes unusually large tab stop values provided by a local attacker. This can lead to an undersized memory buffer, allowing subsequent operations to write beyond its boundaries. Successful exploitation can cause the `unexpand` utility to crash, potentially resulting in a denial of service or enabling further memory manipulation.

A Moderate impact heap-based buffer overflow flaw was found in the `unexpand` utility of GNU coreutils. This vulnerability arises from an integer overflow when processing unusually large tab stop values, leading to an undersized buffer. A local attacker could exploit this by providing crafted input, causing the utility to crash and potentially leading to a denial of service or arbitrary memory manipulation. Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability. Red Hat Enterprise Linux 8 2026-07-29T00:00:00Z RHBA-2026:47115 coreutils-0:8.30-20.el8_10 Red Hat Hardened Images 2026-07-16T00:00:00Z RHSA-2026:40724 coreutils-main-9.11-5.hum1 Red Hat Enterprise Linux 10 Affected coreutils Red Hat Enterprise Linux 6 Out of support scope coreutils Red Hat Enterprise Linux 7 Out of support scope coreutils Red Hat Enterprise Linux 9 Affected coreutils Red Hat OpenShift Container Platform 4 Under investigation rhcos https://www.cve.org/CVERecord?id=CVE-2026-56392 https://nvd.nist.gov/vuln/detail/CVE-2026-56392 https://cert.pl/en/posts/2026/07/CVE-2026-56391 https://git.savannah.gnu.org/cgit/coreutils.git/ https://git.savannah.gnu.org/cgit/coreutils.git/commit/?id=b60a159fdc5bfcf9988d3a4cb6f53abe8ad5d35d