# CVE-2020-36403: Memory corruption in n/a

> An out-of-bounds write in HTSlib allows attackers to execute arbitrary code or cause denial of service via crafted VCF files.

- **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:** 1 Jul 2021
- **Updated:** 4 Aug 2024
- **Also known as:** DEBIAN-CVE-2020-36403, GHSA-9cpm-77gg-x323, OESA-2022-1962, OESA-2022-1963, UBUNTU-CVE-2020-36403, openSUSE-SU-2021:1177-1

## What is CVE-2020-36403?

CVE-2020-36403 is a high-severity memory corruption vulnerability in n/a, published on 1 Jul 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

HTSlib through 1.10.2 allows out-of-bounds write access in vcf_parse_format (called from vcf_parse and vcf_read).

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

## Which versions are affected by CVE-2020-36403?

It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `libhts` | SUSE:Package Hub 15 SP2 | All versions | 1.10.2-bp153.2.5.1 |
| `libhts` | SUSE:Package Hub 15 SP3 | All versions | 1.10.2-bp153.2.5.1 |
| `libhts` | openSUSE:Leap 15.2 | All versions | 1.10.2-bp153.2.5.1 |
| `libhts` | openSUSE:Leap 15.3 | All versions | 1.10.2-bp153.2.5.1 |

Products: Htslib Htslib.

## How do I fix CVE-2020-36403?

Upgrade to a fixed version.

## Is CVE-2020-36403 being exploited?

There is no known exploitation of CVE-2020-36403 in the wild and no public exploit code.

## Other vulnerabilities in n/a

- [CVE-2018-13845](https://insights.sbomify.com/CVE-2018-13845/): Memory corruption in n/a (critical 9.8)
- [CVE-2017-1000206](https://insights.sbomify.com/CVE-2017-1000206/): Memory corruption in n/a (critical 9.8)
- [CVE-2026-31962](https://insights.sbomify.com/CVE-2026-31962/): HTSlib CRAM reader has heap buffer overflow due to improper validation of input (high 8.8)
- [CVE-2026-31963](https://insights.sbomify.com/CVE-2026-31963/): HTSlib CRAM reader has heap buffer overflow due to improper validation of input (high 8.8)
- [CVE-2026-31968](https://insights.sbomify.com/CVE-2026-31968/): HTSlib CRAM decoder vulnerable to buffer overflow (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-36403 and fix it if it is affected.

What it is: CVE-2020-36403 is a high-severity memory corruption vulnerability in n/a, published on 1 Jul 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-2020-36403 in the wild and no public exploit code.

Affected product: n/a. 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-2020-36403/ (Markdown: https://insights.sbomify.com/CVE-2020-36403/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-36403
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-36403
- OSV: https://osv.dev/vulnerability/CVE-2020-36403

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-36403/
Summaries are generated and may contain mistakes; the official description above is the record.