# CVE-2026-56392: Heap-based Buffer Overflow in GNU coreutils

> Attacker can trigger heap overflow via crafted tab stop arguments in unexpand, potentially leading to code execution or crash.

- **Severity:** Low 1.8 (`CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:A/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 24 Jul 2026
- **Updated:** 24 Jul 2026
- **Also known as:** ALSA-2026:66403, CLSA-2026-1788177078, CLSA-2026-1788268556, DEBIAN-CVE-2026-56392, GHSA-g24f-m2hx-pfgx, JLSEC-2026-1196, OESA-2026-3388, OESA-2026-3389, OESA-2026-3390, OESA-2026-3391, OESA-2026-3416, RHBA-2026:47115, RHSA-2026:40724, RHSA-2026:66403, RLSA-2026:66403

## What is CVE-2026-56392?

CVE-2026-56392 is a low-severity vulnerability in GNU coreutils, published on 24 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official 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

Weakness: CWE-122 (Heap-based Buffer Overflow)

## Which versions are affected by CVE-2026-56392?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `coreutils` | AlmaLinux:9 | All versions | 8.32-41.el9_8.1 |
| `coreutils-common` | AlmaLinux:9 | All versions | 8.32-41.el9_8.1 |
| `coreutils-single` | AlmaLinux:9 | All versions | 8.32-41.el9_8.1 |
| `coreutils` | Red Hat:enterprise_linux:8::baseos | All versions | 0:8.30-20.el8_10 |
| `coreutils-common` | Red Hat:enterprise_linux:8::baseos | All versions | 0:8.30-20.el8_10 |
| `coreutils-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:8.30-20.el8_10 |
| `coreutils-debugsource` | Red Hat:enterprise_linux:8::baseos | All versions | 0:8.30-20.el8_10 |
| `coreutils-single` | Red Hat:enterprise_linux:8::baseos | All versions | 0:8.30-20.el8_10 |
| `coreutils-single-debuginfo` | Red Hat:enterprise_linux:8::baseos | All versions | 0:8.30-20.el8_10 |
| `coreutils` | Red Hat:enterprise_linux:9::baseos | All versions | 0:8.32-41.el9_8.1 |
| `coreutils-debuginfo` | Red Hat:enterprise_linux:9::baseos | All versions | 0:8.32-41.el9_8.1 |
| `coreutils-debugsource` | Red Hat:enterprise_linux:9::baseos | All versions | 0:8.32-41.el9_8.1 |
| `coreutils-single` | Red Hat:enterprise_linux:9::baseos | All versions | 0:8.32-41.el9_8.1 |
| `coreutils-single-debuginfo` | Red Hat:enterprise_linux:9::baseos | All versions | 0:8.32-41.el9_8.1 |
| `coreutils` | Red Hat:hummingbird:1 | All versions | 0:9.11-5.hum1 |
| `coreutils-common` | Red Hat:hummingbird:1 | All versions | 0:9.11-5.hum1 |
| `coreutils-single` | Red Hat:hummingbird:1 | All versions | 0:9.11-5.hum1 |
| `coreutils` | Rocky Linux:9 | All versions | 0:8.32-41.el9_8.1 |

Products: Gnu Coreutils.

## How do I fix CVE-2026-56392?

Apply the vendor's patch.

## Is CVE-2026-56392 being exploited?

There is no known exploitation of CVE-2026-56392 in the wild and no public exploit code.

## Other vulnerabilities in GNU coreutils

- [CVE-2015-4042](https://insights.sbomify.com/CVE-2015-4042/): Integer overflow in n/a (critical 9.8)
- [CVE-2015-4041](https://insights.sbomify.com/CVE-2015-4041/): Memory corruption in n/a (high 7.8)
- [CVE-2017-18018](https://insights.sbomify.com/CVE-2017-18018/): Race condition in n/a (high 7.1)
- [CVE-2024-0684](https://insights.sbomify.com/CVE-2024-0684/): Coreutils: heap overflow in split --line-bytes with very long lines (medium 5.5)
- [CVE-2015-1865](https://insights.sbomify.com/CVE-2015-1865/): Race condition in n/a (medium 5.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-56392 and fix it if it is affected.

What it is: CVE-2026-56392 is a low-severity vulnerability in GNU coreutils, published on 24 Jul 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2026-56392 in the wild and no public exploit code.

Affected product: GNU coreutils. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-56392/ (Markdown: https://insights.sbomify.com/CVE-2026-56392/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-56392
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-56392
- OSV: https://osv.dev/vulnerability/CVE-2026-56392

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-56392/
Summaries are generated and may contain mistakes; the official description above is the record.