Vulnerability 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.
CVSS Score
HIGH
Related Weaknesses (CWE)
References
- 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
- https://github.com/php-standard-library/php-standard-library/security/advisories
FAQ
What is CVE-2026-48979?
CVE-2026-48979 is a vulnerability with a CVSS score of 7.5 (HIGH). 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 validat...
How severe is CVE-2026-48979?
CVE-2026-48979 has been rated HIGH with a CVSS base score of 7.5/10. Review the CVSS metrics above for detailed severity breakdown.
Is there a patch for CVE-2026-48979?
Check the references section above for vendor advisories and patch information. Review vendor security bulletins for remediation guidance.