Sr. Software Engineer - .NET

About the Role

We are seeking a Senior Software Engineer (.NET) to join our Never-Ending Support (NES) team. This role focuses on our “NES for .NET” product line, where you will produce critical security patches for CVEs affecting end-of-life versions of .NET and other NuGet packages, as well as build the tooling and automation that makes that work scale.

Key Responsibilities

• Analyze CVEs and upstream security fixes in .NET Runtime, ASP.NET Core, SDK, and related packages, and apply them to end-of-life .NET versions
• Build, test, and reproduce end-of-life .NET versions on modern and legacy toolchains, including resurrecting build environments and pinning dependencies that no longer resolve
• Build and utilize AI-assisted automation for triage, patch analysis, backport drafting, and regression verification, to scale the product securing process.
• Build and maintain test harnesses that validate CVE patch correctness and backwards compatibility
• Provide support to customers' engineering teams on compatibility issues, and upgrade paths

Required Qualifications

• Deep expertise in C#, and the .NET ecosystem. Low-level experience with the .NET Runtime, .NET SDK and other .NET ecosystem projects
• Demonstrated ability to read and reason about unfamiliar low-level code: understanding a security patch well enough to reimplement it against a different code baseline
• Experience building and debugging complex software from source, including toolchain and build-system archaeology
• Experience building software for multiple platforms (Windows, macOS, Linux distributions including RHEL, etc.)
• Strong ownership of correctness and quality – rigorous testing, regression coverage, and an instinct for what a patch might break
• Practical experience using LLMs to automate real engineering work, with judgment about where automation helps and where it can't be trusted
• Comfortable in a small, high-autonomy team where you help shape the process, as much as follow it
• Ability to communicate with customers in early product iterations, or in tier-3 support capacities

Preferred Qualifications

• Contributions to .NET open source projects – dotnet/runtime, dotnet/aspnetcore, or widely used NuGet packages
• Strong grasp of security fundamentals – CVEs, CVSS, common vulnerability classes (deserialization, path traversal, cryptographic misuse, DoS via resource exhaustion), and how to assess exploitability
• Familiarity with container image hardening, SBOMs, artifact signing, and supply chain security
• Experience building and deploying services built on .NET in Microsoft Azure
• Experience as either a technical lead or team lead
• Experience running production services on Azure, AWS and Kubernetes
• Background in security research, vulnerability triage, or product security

At HeroDevs, we believe in the power of diversity, equity, and inclusion to drive innovation, creativity, and success. We are committed to creating a workplace that embraces and celebrates individual differences. We encourage people of all backgrounds and experiences to apply.