# CVE-2020-5235: Out-of-memory condition in Nanopb is potentially exploitable

> An out-of-memory condition in Nanopb can lead to crashes or memory corruption when decoding specific repeated fields, potentially allowing code execution.

- **Severity:** Medium 6.5 (`CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:C/C:L/I:L/A:L`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 4 Feb 2020
- **Updated:** 4 Aug 2024
- **Also known as:** GHSA-6f6v-26gj-6crp, GHSA-gcx3-7m76-287p

## What is CVE-2020-5235?

CVE-2020-5235 is a medium-severity memory corruption vulnerability in Nanopb, published on 4 Feb 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

There is a potentially exploitable out of memory condition In Nanopb before 0.4.1, 0.3.9.5, and 0.2.9.4. When nanopb is compiled with PB_ENABLE_MALLOC, the message to be decoded contains a repeated string, bytes or message field and realloc() runs out of memory when expanding the array nanopb can end up calling `free()` on a pointer value that comes from uninitialized memory. Depending on platform this can result in a crash or further memory corruption, which may be exploitable in some cases. This problem is fixed in nanopb-0.4.1, nanopb-0.3.9.5, nanopb-0.2.9.4.

Weakness: CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2020-5235?

It affects 1 product.


Products: Nanopb Project Nanopb.

## How do I fix CVE-2020-5235?

Upgrade to a fixed version.

## Is CVE-2020-5235 being exploited?

There is no known exploitation of CVE-2020-5235 in the wild and no public exploit code.

## Other vulnerabilities in Nanopb

- [CVE-2014-125106](https://insights.sbomify.com/CVE-2014-125106/): Integer overflow in n/a (critical 9.8)
- [CVE-2020-26243](https://insights.sbomify.com/CVE-2020-26243/): Memory leak in nanopb (high 7.5)
- [CVE-2021-21401](https://insights.sbomify.com/CVE-2021-21401/): Invalid free() call in Nanopb (high 7.1)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2020-5235 and fix it if it is affected.

What it is: CVE-2020-5235 is a medium-severity memory corruption vulnerability in Nanopb, published on 4 Feb 2020. An attacker can exploit it over the internet without logging in, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2020-5235 in the wild and no public exploit code.

Affected product: Nanopb. 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-2020-5235/ (Markdown: https://insights.sbomify.com/CVE-2020-5235/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2020-5235
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2020-5235
- OSV: https://osv.dev/vulnerability/CVE-2020-5235

---
From sbomify Insights: https://insights.sbomify.com/CVE-2020-5235/
Summaries are generated and may contain mistakes; the official description above is the record.