# OSV-2021-251: Heap-buffer-overflow in safe_ltf8_get

> A heap buffer overflow in the CRAM decoder allows attackers to cause crashes or potentially execute code via malicious files.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Not stated
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 30 Jan 2021

## What is OSV-2021-251?

OSV-2021-251 is a memory corruption vulnerability in htslib, published on 30 Jan 2021. 

### Official description

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=30012

```
Crash type: Heap-buffer-overflow READ 1
Crash state:
safe_ltf8_get
cram_const_decode_init
cram_decoder_init
```

## Which versions are affected by OSV-2021-251?

1 open source package ship an affected version, including htslib.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `htslib` | OSS-Fuzz | All versions | None |

## How do I fix OSV-2021-251?

No fix has been published for OSV-2021-251 yet. Limit exposure of the affected software until one is available.

## Is OSV-2021-251 being exploited?

There is no known exploitation of OSV-2021-251 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for OSV-2021-251 and fix it if it is affected.

What it is: OSV-2021-251 is a memory corruption vulnerability in htslib, published on 30 Jan 2021. 
Exploitation: There is no known exploitation of OSV-2021-251 in the wild and no public exploit code.

Affected packages and fixed versions:
- htslib (OSS-Fuzz): affected all versions; no fix listed

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/OSV-2021-251/ (Markdown: https://insights.sbomify.com/OSV-2021-251/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/OSV-2021-251

---
From sbomify Insights: https://insights.sbomify.com/OSV-2021-251/
Summaries are generated and may contain mistakes; the official description above is the record.