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Vulnerability record · CVE-2026-6409 · published 16 April 2026

CVE-2026-6409: Improper input validation vulnerability

A Denial of Service (DoS) vulnerability exists in the Protobuf PHP library during the parsing of untrusted input. Maliciously structured messages—specifically those containing negative varints or deep recursion—can be used to crash the application, impacting service availability.

7.1 CVSS 4.0 High EPSS 0.43% · top 65.5% CWE-20 · Improper input validation Awaiting Analysis
7.1CVSS 4.0 base score
0.43%EPSS exploitation probability, 30 days
NoNot in CISA KEV
0Affected product versions listed by NVD
1References
17 Jun 2026Last modified by NVD

Description

A Denial of Service (DoS) vulnerability exists in the Protobuf PHP library during the parsing of untrusted input. Maliciously structured messages—specifically those containing negative varints or deep recursion—can be used to crash the application, impacting service availability.

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:

References

LinkTags
https://github.com/protocolbuffers/protobuf/security/advisories/GHSA-p2gh-cfq4-4wjc

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Source: NIST National Vulnerability Database (record CVE-2026-6409), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.