# CVE-2021-39537: Memory corruption in n/a

> A heap-based buffer overflow in ncurses allows attackers to execute arbitrary code or cause denial of service via crafted terminfo data.

- **Severity:** High 8.8 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 20 Sep 2021
- **Updated:** 8 Oct 2026
- **Also known as:** ALPINE-CVE-2021-39537, AZL-6740, CLEANSTART-2026-RK36716, DEBIAN-CVE-2021-39537, GHSA-v5gv-3mwr-6223, JLSEC-2026-451, OESA-2021-1386, SUSE-SU-2021:3490-1, SUSE-SU-2021:3491-1, UBUNTU-CVE-2021-39537, openSUSE-SU-2021:1417-1, openSUSE-SU-2021:3490-1

## What is CVE-2021-39537?

CVE-2021-39537 is a high-severity memory corruption vulnerability in Apple Mac Os X, published on 20 Sep 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.

### Official description

An issue was discovered in ncurses through v6.2-1. _nc_captoinfo in captoinfo.c has a heap-based buffer overflow.

Weakness: CWE-787 (Out-of-bounds Write)

## Which versions are affected by CVE-2021-39537?

It affects 3 products.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `ncurses` | SUSE:Linux Enterprise Micro 5.0 | All versions | 6.1-5.9.1 |
| `ncurses` | SUSE:Linux Enterprise Micro 5.1 | All versions | 6.1-5.9.1 |
| `ncurses` | SUSE:Linux Enterprise Module for Basesystem 15 SP2 | All versions | 6.1-5.9.1 |
| `ncurses` | SUSE:Linux Enterprise Module for Basesystem 15 SP3 | All versions | 6.1-5.9.1 |
| `ncurses` | SUSE:Linux Enterprise Module for Development Tools 15 SP2 | All versions | 6.1-5.9.1 |
| `ncurses` | SUSE:Linux Enterprise Module for Development Tools 15 SP3 | All versions | 6.1-5.9.1 |
| `ncurses` | SUSE:Linux Enterprise Module for Legacy 15 SP2 | All versions | 6.1-5.9.1 |
| `ncurses` | SUSE:Linux Enterprise Module for Legacy 15 SP3 | All versions | 6.1-5.9.1 |
| `ncurses` | SUSE:Linux Enterprise Server 12 SP5 | All versions | 5.9-75.1 |
| `ncurses` | SUSE:Linux Enterprise Server for SAP Applications 12 SP5 | All versions | 5.9-75.1 |
| `ncurses` | SUSE:Linux Enterprise Software Development Kit 12 SP5 | All versions | 5.9-75.1 |
| `ncurses` | openSUSE:Leap 15.2 | All versions | 6.1-lp152.8.3.1 |
| `ncurses` | openSUSE:Leap 15.3 | All versions | 6.1-5.9.1 |

Products: Apple Mac Os X, Apple Macos, Invisible-Island Ncurses.

## How do I fix CVE-2021-39537?

Apply the vendor's patch.

## Is CVE-2021-39537 being exploited?

There is no known exploitation of CVE-2021-39537 in the wild and no public exploit code.

## Other vulnerabilities in Apple Mac Os X

- [CVE-2014-7169](https://insights.sbomify.com/CVE-2014-7169/): GNU Bourne-Again Shell (Bash) Arbitrary Code Execution (critical 9.8, exploited in the wild)
- [CVE-2014-6271](https://insights.sbomify.com/CVE-2014-6271/): GNU Bourne-Again Shell (Bash) Arbitrary Code Execution (critical 9.8, exploited in the wild)
- [CVE-2012-1823](https://insights.sbomify.com/CVE-2012-1823/): PHP-CGI Query String Parameter (critical 9.8, exploited in the wild)
- [CVE-2021-30713](https://insights.sbomify.com/CVE-2021-30713/): Apple macOS Unspecified (high 7.8, exploited in the wild)
- [CVE-2019-8526](https://insights.sbomify.com/CVE-2019-8526/): Apple macOS Use-After-Free (high 7.8, exploited in the wild)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2021-39537 and fix it if it is affected.

What it is: CVE-2021-39537 is a high-severity memory corruption vulnerability in Apple Mac Os X, published on 20 Sep 2021. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Exploitation: There is no known exploitation of CVE-2021-39537 in the wild and no public exploit code.

Affected product: Apple Mac Os X. 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-2021-39537/ (Markdown: https://insights.sbomify.com/CVE-2021-39537/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2021-39537
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2021-39537
- OSV: https://osv.dev/vulnerability/CVE-2021-39537

---
From sbomify Insights: https://insights.sbomify.com/CVE-2021-39537/
Summaries are generated and may contain mistakes; the official description above is the record.