CVE-2026-6409

Denial of Service (DoS) vulnerability exists in the Protobuf PHP library during the parsing of untrusted input

HIGH

7.1

CVSS Score

Published: April 16, 2026 at 02:30 PM UTC

Updated: October 26, 2026 at 09:10 PM UTC

1 product affected across 1 vendorProtobuf PHP

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Severity

HIGH7.1

Exploit prediction

EPSS 0.4%

SSVC

No known exploit

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.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

Protobuf PHP · Protocolbuffers

60%

v < 4.33.6v < 5.34.0-RC1

Affected range stops below 4.33.6, so it looks safe — our inference, not a vendor statement

Affected range stops below 5.34.0-RC1, so it looks safe — our inference, not a vendor statement

Remediation

No guide yet

No remediation guidance has been written for this CVE yet, and no fixed version or vendor advisory is recorded against it.

References (1)

Source: cverecord

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

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

7.1HIGHGoogle

Vector?

Quick Info

StatusAWAITING ANALYSIS

CWE

CWE-20

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