🛡️ CVE-2026-6409 on Debian — protobuf

⚪ Unknown ✅ No Known Exploit OSV
N/A
CVSS Score
0 Low4 Medium7 High9 Critical10

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.

Distribution advisory

This page covers CVE-2026-6409 as tracked by Debian, for the package protobuf. The fix is available in version 3.21.12-16; earlier versions remain affected.

How this vulnerability can be exploited

This issue can be reached over the network, attack complexity is low, an attacker needs no privileges on the target. A user must be tricked into taking some action. The scope is unchanged, so the impact stays within the vulnerable component. Rated impact: confidentiality none, integrity none, availability high.

Weakness class

DEBIAN-CVE-2026-6409 is classified as CWE-400: Uncontrolled Resource Consumption. A request can consume memory, CPU or storage without limit, exhausting capacity for everyone else.

Affected software

DEBIAN-CVE-2026-6409 is recorded against 1 package.

  • protobuf (fixed in 3.21.12-16)

Timeline and source

Published on 16 April 2026 and last revised on 4 August 2026. No public exploit is currently recorded for this entry. Record sourced from OSV.

References

security-tracker.debian.org (Advisory)

CVE-2026-6409 on other distributions

Each distribution ships its own build and its own fixed version. Pick the one you run:

Details

Severity Unknown
CVSS Score N/A
CVSS 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/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:X/V:X/RE:X/U:X
CWE N/A
Public Exploit ✅ No
Source OSV
Published 2026-04-16
Updated 2026-08-20
Modified 2026-08-04
Fix URL N/A

Affected Packages

Software From version Fixed in
protobuf — 3.21.12-16

Similar Threats

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