# OSV-2021-1127: Heap-use-after-free in zebra_nhg_hash_equal

> A heap-use-after-free in the Zebra daemon's next-hop group hash lookup can cause crashes or potential code execution, affecting network routing infrastructure.

- **Severity:** Not scored
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 15 Aug 2021

## What is OSV-2021-1127?

OSV-2021-1127 is an use after free vulnerability in frr, published on 15 Aug 2021. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

OSS-Fuzz report: https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=37164

```
Crash type: Heap-use-after-free READ 4
Crash state:
zebra_nhg_hash_equal
hash_get
hash_lookup
```

## Which versions are affected by OSV-2021-1127?

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


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

## How do I fix OSV-2021-1127?

No fix has been published for OSV-2021-1127 yet. Limit exposure of the affected software until one is available.

## Is OSV-2021-1127 being exploited?

There is no known exploitation of OSV-2021-1127 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for OSV-2021-1127 and fix it if it is affected.

What it is: OSV-2021-1127 is an use after free vulnerability in frr, published on 15 Aug 2021. It can only be exploited from the same machine or local network, with no action from the victim.
Exploitation: There is no known exploitation of OSV-2021-1127 in the wild and no public exploit code.

Affected packages and fixed versions:
- frr (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-2021-1127/ (Markdown: https://insights.sbomify.com/OSV-2021-1127/index.md)
```

## Sources

- OSV: https://osv.dev/vulnerability/OSV-2021-1127

---
From sbomify Insights: https://insights.sbomify.com/OSV-2021-1127/
Summaries are generated and may contain mistakes; the official description above is the record.