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CVE-2026-48979

HIGHCVSS 7.5/10EPSS 0.27%

Last modified

CVE-2026-48979 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. 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. EPSS estimates a 0.27% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1
7.5/10

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

EPSS Probability
0.27%

18.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

Source: CNA advisory (CVE.org). NVD analysis pending.

VendorProductVersions
php-standard-libraryphp-standard-library>= 6.1.0, < 6.1.2; >= 6.2.0, < 6.2.1
php-standard-libraryphp-standard-library/h2>= 6.1.0, < 6.1.2; >= 6.2.0, < 6.2.1

References

Timeline

Published
Last Modified
Status
Awaiting Analysis

Frequently Asked Questions

What is CVE-2026-48979?
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.
How severe is CVE-2026-48979?
CVE-2026-48979 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 0.27% probability of exploitation in the next 30 days.
How do I fix CVE-2026-48979?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST