CVE-2026-48979 PHP Standard Library: HTTP/2 server-side missing content-length validation enables request smuggling
Attackers can exploit missing content-length validation in the PHP Standard Library HTTP/2 server to perform request smuggling, bypassing application security controls.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-48979?
CVE-2026-48979 is a high-severity vulnerability in php-standard-library, published on 17 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official 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.
Weakness: CWE-444
Which versions are affected by CVE-2026-48979?
8 open source packages ship an affected version, including php-standard-library/h2 and php-standard-library/php-standard-library.
| Package | Affected | Fixed in |
|---|---|---|
php-standard-library/h2 Packagist | From 6.1.0 | 6.1.2 |
php-standard-library/h2 Packagist | From 6.1.0 | 6.1.2 |
php-standard-library/h2 Packagist | From 6.2.0 | 6.2.1 |
php-standard-library/h2 Packagist | From 6.2.0 | 6.2.1 |
php-standard-library/php-standard-library Packagist | From 6.1.0 | 6.1.2 |
php-standard-library/php-standard-library Packagist | From 6.1.0 | 6.1.2 |
2 more packages
php-standard-library/php-standard-library Packagist | From 6.2.0 | 6.2.1 |
php-standard-library/php-standard-library Packagist | From 6.2.0 | 6.2.1 |
How do I fix CVE-2026-48979?
Upgrade php-standard-library/h2 to a fixed version for your release line: 6.1.2 or 6.2.1.
Is CVE-2026-48979 being exploited?
There is no known exploitation of CVE-2026-48979 in the wild and no public exploit code.
Sources
Also known as GHSA-pw9p-jvrm-f7rm.