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Vulnerability record · CVE-2026-48979 · published 17 June 2026

CVE-2026-48979: HTTP request smuggling vulnerability

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.

7.5 CVSS 3.1 High EPSS 0.46% · top 62.6% CWE-444 · HTTP request smuggling Awaiting Analysis
7.5CVSS 3.1 base score
0.46%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
3References
23 Jun 2026Last modified by NVD

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:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

References

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Related vulnerabilities

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Source: NIST National Vulnerability Database (record CVE-2026-48979), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.