CVE-2026-48979High· 7.5▾ TwilightPHP Standard Library: HTTP/2 server-side missing content-length validation enables request smuggling
▾ Twilight zone — High severity, or a signal on a lesser flaw
impact 41.3 · likelihood 0.1 · exploitation 0
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Exploit-prediction probability, daily snapshots since Jul 30.
Disclosure to exploitation, from the record and what we observed since indexing it.
Disclosed via GHSA
0.3%
0.3% → 0.5%
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:
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.
content-length header on incoming HEADERS (server-side only — clients do not enforce this per RFC 9110 §9.3.2).StreamException on mismatch or overflow.Regression tests landed in #781, 9 of the new tests fail against the pre-fix code, proving the validation boundary is enforced.
None at the protocol layer. Applications using Psl\H2\ServerConnection directly should upgrade.
php-standard-library/h2 >= 6.1.0, < 6.1.2php-standard-library/h2 >= 6.2.0, < 6.2.1php-standard-library/php-standard-library >= 6.1.0, < 6.1.2php-standard-library/php-standard-library >= 6.2.0, < 6.2.1Upgrade to a patched release:
php-standard-library/h2 6.1.2php-standard-library/h2 6.2.1php-standard-library/php-standard-library 6.1.2php-standard-library/php-standard-library 6.2.1Connected by shared product, vendor, weakness, or advisory.
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