# CVE-2026-116742: HTSlib through 1.24 Heap Out-of-Bounds Write via Truncated .gzi Index Count


- **Severity:** Medium 4.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:N/UI:P/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N`)
- **Exploited in the wild:** Not known
- **Fix available:** No
- **Published:** 26 Oct 2026
- **Updated:** 27 Oct 2026
- **Also known as:** DEBIAN-CVE-2026-116742, GHSA-r296-8jjg-794r, UBUNTU-CVE-2026-116742

## What is CVE-2026-116742?

CVE-2026-116742 is a medium-severity vulnerability in samtools htslib, published on 26 Oct 2026. 

### Official description

HTSlib through 1.24 contains a heap out-of-bounds write and read vulnerability in bgzf_index_load_hfile() in bgzf.c that allows attackers to corrupt heap memory by supplying a crafted .gzi index entry count. A count of 0xFFFFFFFF truncates noffs to zero, causing writes past a malloc(0) buffer and an offs[-1] read in bgzf_useek(), resulting in heap corruption or crashes in tools like samtools and bcftools.

Weakness: CWE-197 (Numeric Truncation Error)

## Which versions are affected by CVE-2026-116742?


## How do I fix CVE-2026-116742?

No fix has been published for CVE-2026-116742 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-116742 being exploited?

There is no known exploitation of CVE-2026-116742 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-116742 and fix it if it is affected.

What it is: CVE-2026-116742 is a medium-severity vulnerability in samtools htslib, published on 26 Oct 2026. 
Exploitation: There is no known exploitation of CVE-2026-116742 in the wild and no public exploit code.

Affected product: samtools htslib. 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-2026-116742/ (Markdown: https://insights.sbomify.com/CVE-2026-116742/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-116742
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-116742
- OSV: https://osv.dev/vulnerability/CVE-2026-116742

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-116742/
Summaries are generated and may contain mistakes; the official description above is the record.