# OSV-2021-745: Heap-buffer-overflow in skip_to_next_entry

> A heap-buffer-overflow in the Python interpreter's exception handling allows attackers to cause crashes or potentially execute arbitrary code.

- **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:** 11 May 2021

## What is OSV-2021-745?

OSV-2021-745 is a memory corruption vulnerability in cpython3, published on 11 May 2021. 

### Official description

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=34110

```
Crash type: Heap-buffer-overflow READ 1
Crash state:
skip_to_next_entry
get_exception_handler
_PyEval_EvalFrameDefault
```

## Which versions are affected by OSV-2021-745?

1 open source package ship an affected version, including cpython3.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `cpython3` | OSS-Fuzz | All versions | None |

## How do I fix OSV-2021-745?

No fix has been published for OSV-2021-745 yet. Limit exposure of the affected software until one is available.

## Is OSV-2021-745 being exploited?

There is no known exploitation of OSV-2021-745 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for OSV-2021-745 and fix it if it is affected.

What it is: OSV-2021-745 is a memory corruption vulnerability in cpython3, published on 11 May 2021. 
Exploitation: There is no known exploitation of OSV-2021-745 in the wild and no public exploit code.

Affected packages and fixed versions:
- cpython3 (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-2021-745/ (Markdown: https://insights.sbomify.com/OSV-2021-745/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/OSV-2021-745

---
From sbomify Insights: https://insights.sbomify.com/OSV-2021-745/
Summaries are generated and may contain mistakes; the official description above is the record.