Develop security patches for CVEs affecting end-of-life .NET versions and NuGet packages. Analyze upstream fixes, rebuild legacy .NET environments, maintain cross-platform toolchains, and create test harnesses for patch correctness and compatibility. Build AI-assisted automation for vulnerability triage and backporting, support customer engineering teams, and contribute to security, supply-chain, and cloud-related initiatives.
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
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