# CVE-2026-5758: protocol-buffers RCE — Fixed in 3.6.1 📦 📦 npm Not in CISA KEV MEDIUM severity # CVE-2026-5758 — protocol-buffers-schema MEDIUM [Fix: mafintosh/protocol-buffers-schema#70](https://github.com/mafintosh/protocol-buffers-schema/pull/70) CVE-2026-5758 is a medium-severity (CVSS 6.5) remote code execution vulnerability in protocol-buffers-schema. A fix is available for protocol-buffers-schema — see the affected versions and patch details below. Mafintosh's protocol-buffers-schema is vulnerable to prototype pollution Also known as[GHSA-j452-xhg8-qg39](/vulnerability/GHSA-j452-xhg8-qg39) Published Apr 15, 2026 Updated Oct 28, 2026 Affected 1 pkg Patched 1 / 1 Exploits None indexed Exploitation data as of Nov 7, 2026 · OSV.dev, NVD, FIRST.org (EPSS) ## Exploitation Status ### Proof-of-concept exploit code exists - CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation. Exploitation and automatability from CISA’s SSVC triage for CVE-2026-5758. ## EPSS Exploitation Probability [via FIRST.org ↗](https://www.first.org/epss/) 0.5%probability of exploitation in next 30 days Lower Risk0.00% Lower risk than most CVEs45th percentile — riskier than 45% of all scored CVEsHighest risk 0.00%0.40%0.79%1.19%0.2%0.5%May 26Sep 26Nov 26 Probability of exploitation in the next 30 days, from [FIRST.org EPSS](https://www.first.org/epss/). ## How urgent is this, really ## Where this sits among everything scored ## Real-World Exposure 1 pkg affected How broadly this vulnerability is actually deployed: weekly install volume shows current usage, and reverse-dependency count shows how many other packages break if it stays unpatched. 69other npm packages depend on this — each one inherits the vulnerability until it's patched upstream `protocol-buffers-schema`npm 14.9Mdownloads / week ## Description JavaScript is vulnerable to prototype pollution in Mafintosh's protocol-buffers-schema Version 3.6.0, where an attacker may alter the application logic, bypass security checks, cause a DoS or achieve remote code execution. ## Affected Packages 1 total 1 fixed Ecosystem Package Vulnerable range Fix 📦npm `protocol-buffers-schema` all versions 3.6.1`npm install protocol-buffers-schema@3.6.1` ## Detection & mitigation playbook Open-source dependency 1. ### Detect Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for protocol-buffers-schema, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version. 2. ### Fix Update protocol-buffers-schema to 3.6.1 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-5758 is resolved across your whole dependency graph. 3. ### Workarounds Cap what an attacker can consume: apply request size, rate and timeout limits in front of the affected component, and run it with memory and CPU limits so exhaustion degrades one worker rather than the whole service. ## Fixing This On Your OS If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project. Red HatModerate Red Hat rates this flaw as Moderate. \`protocol-buffers-schema\` is a library and does not run on its own, as such, it requires an application to call it and utilize the vulnerable parsing functionality. When the pollution occurs, that application may read whatever malicious property was injected by the attacker, but… Workaround published by Red Hat > If using protocol-buffers-schema, perform the following checks to help mitigate the impact of this vulnerability: 1. Do not parse \`.proto\` files from untrusted or semi-trusted sources (ex. user uploads, external repos, third-party APIs, etc.). 2. Audit downstream code for prototype pollution gadgets (ex. template engines, ORM configs, HTTP frameworks). 3. Consider freezing \`Object.prototype\` in security-sensitive contexts as a defense-in-depth measure (ex. \`Object.freeze(Object.prototype);\`). If maintaining a parser or config loader: 1. Never use \`reduce\` or bracket notation to walk user-controlled paths without filtering dangerous keys. 2. Block \`\_\_proto\_\_\`, \`constructor\`, and… Source: [Red Hat security advisory for CVE-2026-5758](https://access.redhat.com/security/cve/cve-2026-5758) (CC BY 4.0) ## Frequently Asked Questions JavaScript is vulnerable to prototype pollution in Mafintosh's protocol-buffers-schema Version 3.6.0, where an attacker may alter the application logic, bypass security checks, cause a DoS or achieve remote code execution. O3 Security · Impact-Aware SCA ### Is CVE-2026-5758 in your dependencies? Find it across npm, including transitive dependencies. [Scan my dependencies](/book-demo) [How O3 SCA works](/impact-aware-sca)