CVE-2026-6409

Publication date 16 April 2026

Last updated 20 October 2026

Ubuntu priority

Medium

Why this priority?

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.

Status

Package Ubuntu Release Status
protobuf 26.10 stonking
Not affected
26.04 LTS resolute
Vulnerable
25.10 questing Ignored end of life, was needed
24.04 LTS noble
Vulnerable
22.04 LTS jammy
Not affected
20.04 LTS focal
Not affected
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty
Not affected

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
protobuf

Severity score breakdown

CVSS version: CVSS v4.0

Base score 7.1 · High

Vector: 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

References

Related Ubuntu Security Notices (USN)

    • USN-8943-1
    • Protocol Buffers vulnerability
    • 20 October 2026

Other references

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