Browser Security Engineer

Cintrifuse; San Francisco (CA); On-site; USD 150,000 - 210,000; Full time

Benefits offered by this job

Industry-competitive salary

Equity

Medical + dental coverage

Dependent coverage

Relocation assistance

Unlimited PTO

401k + company match

Job summary

Kernel is a fast, open source browser infrastructure for AI agents, handling autoscaling and secure isolation. We’re building a Chromium-based runtime used by developers to run thousands of concurrent web interactions with reproducible builds.

We’re seeking a Browser Security Engineer to harden the runtime, focusing on sandboxing, networking, and microVM isolation. You’ll work with low-level tools to debug, patch, and optimize Chromium within Kernel’s infrastructure and collaborate with a senior

Qualifications

• Deep familiarity with Chromium internals or browser sandboxes.
• Experience with Linux kernel, microVMs, or container isolation.
• Strong debugging skills with low-level tools (strace, gdb, perf).

Responsibilities

• Debug, patch, and optimize Chromium builds in Kernel’s microVM environments.
• Implement and maintain network isolation, proxy routing, and IP handling for browsers.
• Collaborate with infra engineers on unikernel-based isolation and kernel security policies.
• Build internal tooling for binary analysis, crash triage, and vulnerability monitoring.
• Support secure supply chain and reproducible builds for browser images.

Skills

Chromium internals

Browser sandboxes

Renderer/network stacks

Linux kernel

microVMs

low-level debugging

networking basics

Tools

strace

gdb

perf

Job description

About KernelKernel is crazy fast, open source browser infrastructure for AI agents. We handle autoscaling, observability, and the messy details of web interaction, so developers can focus on what their agents do instead of how they do it.Teams at Cash App, Framer, and 7000+ others use Kernel for deep research, QA automation, and real-time web analysis. We've raised $22M from Accel, YC, and Vercel.If you're interested in building critical infrastructure for agents on the web, we'd love to chat.

About the role

We’re hiring a Browser Security Engineer to harden and extend our Chromium-based browser runtime. You’ll work at the intersection of sandboxing, networking, and virtualization — ensuring our browsers run securely and efficiently across thousands of concurrent users.

What you’ll do

• Debug, patch, and optimize Chromium builds running inside Kernel’s microVM environments.
• Implement and maintain network isolation, proxy routing, and IP handling for browsers.
• Collaborate with infra engineers on unikernel-based isolation, process scheduling, and kernel security policies.
• Build internal tooling for binary analysis, crash triage, and vulnerability monitoring.
• Support the team in maintaining secure supply chain and reproducible builds for our browser images.

What we’re looking for

• Deep familiarity with Chromium internals, browser sandboxes, or renderer/network stacks.
• Experience with Linux kernel, microVMs (Firecracker, Cloud-Hypervisor, Kata, gVisor, etc.), or container isolation.
• Strong debugging skills with strace, gdb, perf, or similar low-level tools.
• Knowledge of networking fundamentals (DNS, TCP/IP, NAT, proxies, TLS).
• Background in security engineering or browser hardening a plus.

What you can expect as a Kernel

Industry-competitive salaryAbove market equityPremium medical + dental coverage + dependent coverageSmall, trusting team of senior + staff engineersDefault async with minimal bureaucracyDaily lunches on usUnlimited PTO401k + company matchRelocation assistance

Hiring process

We have a simple process focused on real world collaboration and jointly getting to know each other:30 minute intro calls with one of Kernel’s co-founders 45-minute technical interview (virtual)Half-day on-site (in-person) working with our team on relevant technical challenges.Offer!