# CVE-2026-2016: happyfish100 libfastcommon base64.c base64_decode stack-based overflow

> A stack-based buffer overflow in libfastcommon's base64 decoder allows local attackers to execute arbitrary code or cause denial of service.

- **Severity:** Medium 4.8 (`CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Local or same network only
- **Victim action needed:** Not needed
- **Fix available:** No
- **Published:** 6 Feb 2026
- **Updated:** 23 Feb 2026
- **Also known as:** GHSA-v5g8-2q7f-c524

## What is CVE-2026-2016?

CVE-2026-2016 is a medium-severity memory corruption vulnerability in happyfish100 libfastcommon, published on 6 Feb 2026. It can only be exploited from the same machine or local network, with no action from the victim.

### Official description

A security vulnerability has been detected in happyfish100 libfastcommon up to 1.0.84. Affected by this vulnerability is the function base64_decode of the file src/base64.c. The manipulation leads to stack-based buffer overflow. Local access is required to approach this attack. The exploit has been disclosed publicly and may be used. The identifier of the patch is 82f66af3e252e3e137dba0c3891570f085e79adf. Applying a patch is the recommended action to fix this issue.

Weakness: CWE-121 (Stack-based Buffer Overflow), CWE-787 (Out-of-bounds Write), CWE-119 (Improper Restriction of Operations within the Bounds of a Memory Buffer)

## Which versions are affected by CVE-2026-2016?

It affects 1 product.


Products: Happyfish100 Libfastcommon.

## How do I fix CVE-2026-2016?

No fix has been published for CVE-2026-2016 yet. Limit exposure of the affected software until one is available.

## Is CVE-2026-2016 being exploited?

There is no known exploitation of CVE-2026-2016 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-2016 and fix it if it is affected.

What it is: CVE-2026-2016 is a medium-severity memory corruption vulnerability in happyfish100 libfastcommon, published on 6 Feb 2026. 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 CVE-2026-2016 in the wild and no public exploit code.

Affected product: happyfish100 libfastcommon. 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-2026-2016/ (Markdown: https://insights.sbomify.com/CVE-2026-2016/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-2016
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-2016
- OSV: https://osv.dev/vulnerability/CVE-2026-2016

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-2016/
Summaries are generated and may contain mistakes; the official description above is the record.