CVE-2026-56392
Received Received - Intake

Heap-based Buffer Overflow in GNU coreutils unexpand

Publication date: 2026-07-24

Last updated on: 2026-07-24

Assigner: CERT.PL

Description
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

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Meta Information

Published
2026-07-24
Last Modified
2026-07-24
Generated
2026-07-24
AI Q&A
2026-07-24
EPSS Evaluated
N/A
NVD
CVE-2026-56392
EUVD
EUVD-2026-48525

Affected Vendors & Products

Showing 1 associated CPE
Vendor Product Version / Range
gnu coreutils From 1.0.0 (inc)

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Exploitability

CWE
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KEV
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CWE ID Description
CWE-122 A heap overflow condition is a buffer overflow, where the buffer that can be overwritten is allocated in the heap portion of memory, generally meaning that the buffer was allocated using a routine such as malloc().

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Executive Summary

CVE-2026-56392 is a heap-based buffer overflow in GNU coreutils' unexpand utility caused by an integer overflow during buffer allocation. When processing large tab stop (-t) values, the multiplication for allocation size wraps around, creating an undersized buffer. This leads to out-of-bounds heap writes when processing crafted input, potentially causing crashes or enabling heap write primitives depending on memory layout.

Detection Guidance

To detect this vulnerability, check the version of GNU coreutils on your system. Run 'unexpand --version' to see if it is affected. If your version is below the patched commit b60a159fdc5bfcf9988d3a4cb6f53abe8ad5d35d, it may be vulnerable. Test with large tab stop values using 'unexpand -t 1000000000000000000000000 /path/to/file' to see if it crashes or behaves abnormally.

Impact Analysis

An attacker could exploit this to crash the unexpand utility or potentially execute arbitrary code on your system by providing specially crafted input with large tab stop values. This could lead to denial of service or compromise of the affected system if unexpand is used in automated or privileged contexts.

Mitigation Strategies

Immediately update GNU coreutils to a version that includes the fix from commit b60a159fdc5bfcf9988d3a4cb6f53abe8ad5d35d. If updating is not possible, avoid using the unexpand command with large tab stop (-t) values until patched. Monitor system logs for crashes in unexpand as a potential indicator of exploitation.

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