High, CVSS 7.5PackagistPublished
PHP Standard Library: HTTP/2 server-side missing content-length validation enables request smuggling
CVE-2026-48979 · GHSA-pw9p-jvrm-f7rm
- Affected
- Packagist php-standard-library/h2 >= 6.1.0, < 6.1.2; >= 6.2.0, < 6.2.1
- Fixed in
- 6.2.16.1.2· Vendor fix available
- Issue
- Impact Psl\H2\ServerConnection does not validate that the total bytes received in DATA frames match the content-length header declared in the HEADERS frame, in violation of RFC 9113 §8.1.1. A malicious client can: - Send more DATA bytes than declared, smuggling additional content past application-level size limits. - 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. The high-level Psl\HTTP\Server is in active development and was not yet released at the time of this advisory; consumers of documented high-level PSL APIs are not affected. Patches Fixed in 6.1.2 and 6.2.1. - Parses and validates the content-length header on incoming HEADERS (server-side only — clients do not enforce this per RFC 9110 §9.3.2). - Tracks cumulative DATA frame payload length per stream. - Throws…
Recommended action: Upgrade to 6.2.1 or 6.1.2 by release line, then redeploy and verify.A vendor fix does not resolve your finding until you verify it in your own systems.