CVE-2026-6409 | Protocol Buffers Protobuf-php up to 4.33.5/5.33.x Structured Message denial of service (GHSA-p2gh-cfq4-4wjc / EUVD-2026-23268)

VDB-357929 · CVE-2026-6409 · GHSA-P2GH-CFQ4-4WJC PROTOCOL BUFFERS PROTOBUF-PHP UP TO 4.33.5/5.33.X STRUCTURED MESSAGE DENIAL OF SERVICE HISTORYDIFFRELATEJSONXMLCTI CVSS Meta Temp Score Current Exploit Price (≈) CTI Interest Score 5.1 $0-$5k 2.88 Summaryinfo A vulnerability was found in Protocol Buffers Protobuf-php up to 4.33.5/5.33.x. It has been classified as problematic. Affected by this vulnerability is an unknown functionality of the component Structured Message Handler. The manipulation leads to denial of service. This vulnerability is traded as CVE-2026-6409. It is possible to initiate the attack remotely. There is no exploit available. Upgrading the affected component is recommended. Detailsinfo A vulnerability was found in Protocol Buffers Protobuf-php up to 4.33.5/5.33.x. It has been rated as problematic. This issue affects an unknown code block of the component Structured Message Handler. The manipulation with an unknown input leads to a denial of service vulnerability. Using CWE to declare the problem leads to CWE-404. The product does not release or incorrectly releases a resource before it is made available for re-use. Impacted is availability. The summary by CVE is: 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. The weakness was shared by 34selen as GHSA-p2gh-cfq4-4wjc. The advisory is shared at github.com. The identification of this vulnerability is CVE-2026-6409 since 04/15/2026. The exploitation is known to be easy. The attack may be initiated remotely. No form of authentication is needed for a successful exploitation. Neither technical details nor an exploit are publicly available. MITRE ATT&CK project uses the attack technique T1499 for this issue. Upgrading to version 4.33.6 or 5.34.0-RC1 eliminates this vulnerability. The vulnerability is also documented in the vulnerability database at EUVD (EUVD-2026-23268). Productinfo Type Programming Language Software Vendor Protocol Buffers Name Protobuf-php Version 4.33.0 4.33.1 4.33.2 4.33.3 4.33.4 4.33.5 5.0 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10 5.11 5.12 5.13 5.14 5.15 5.16 5.17 5.18 5.19 5.20 5.21 5.22 5.23 5.24 5.25 5.26 5.27 5.28 5.29 5.30 5.31 5.32 5.33 CPE 2.3info 🔒 🔒 🔒 CPE 2.2info 🔒 🔒 🔒 CVSSv4info VulDB Vector: 🔒 VulDB Reliability: 🔍 CNA CVSS-B Score: 🔒 CNA CVSS-BT Score: 🔒 CNA Vector: 🔒 CVSSv3info VulDB Meta Base Score: 5.3 VulDB Meta Temp Score: 5.1 VulDB Base Score: 5.3 VulDB Temp Score: 5.1 VulDB Vector: 🔒 VulDB Reliability: 🔍 CVSSv2info Vector Complexity Authentication Confidentiality Integrity Availability Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock Unlock VulDB Base Score: 🔒 VulDB Temp Score: 🔒 VulDB Reliability: 🔍 Exploitinginfo Class: Denial of service CWE: CWE-404 CAPEC: 🔒 ATT&CK: 🔒 Physical: No Local: No Remote: Yes Availability: 🔒 Status: Not defined Price Prediction: 🔍 Current Price Estimation: 🔒 0-Day Unlock Unlock Unlock Unlock Today Unlock Unlock Unlock Unlock Threat Intelligenceinfo Interest: 🔍 Active Actors: 🔍 Active APT Groups: 🔍 Countermeasuresinfo Recommended: Upgrade Status: 🔍 0-Day Time: 🔒 Upgrade: Protobuf-php 4.33.6/5.34.0-RC1 Timelineinfo 04/15/2026 CVE reserved 04/16/2026 +1 days Advisory disclosed 04/16/2026 +0 days VulDB entry created 04/16/2026 +0 days VulDB entry last update Sourcesinfo Advisory: GHSA-p2gh-cfq4-4wjc Researcher: 34selen Status: Confirmed CVE: CVE-2026-6409 (🔒) GCVE (CVE): GCVE-0-2026-6409 GCVE (VulDB): GCVE-100-357929 EUVD: 🔒 Entryinfo Created: 04/16/2026 18:23 Updated: 04/16/2026 19:10 Changes: 04/16/2026 18:23 (70), 04/16/2026 19:10 (1) Complete: 🔍 Cache ID: 99:FC9:101 Discussion No comments yet. Languages: en. Please log in to comment. ◂ PreviousOverviewNext ▸