Senior Penetration Engineer (5G & Protocol Security)

CACI; United States; On-site; USD 113,000 - 238,000; Full time

Job summary

CACI is seeking a Senior Penetration Engineer (5G & Protocol Security) to lead advanced security assessments of telecom systems. You will reverse‑engineer closed binaries, develop stateful fuzzers, and map complex 5G authentication flows while reporting actionable findings to engineering teams.

The role emphasizes deep protocol knowledge, hands-on binary analysis, and tool development in Python/C++. A US citizenship and ability to obtain a security clearance are required, with up to 10% travel

Qualifications

• 7+ years of vulnerability research, protocol analysis, or reverse engineering.
• Deep understanding of 5G/4G architecture and 3GPP security standards.
• Knowledge of telecom protocol stacks, signaling, management and data plane components.
• Experience with Linux kernel internals or RTOS used in telecom hardware.
• Hands-on experience with disassembly/decompilation tools and hardware debugging.
• US citizenship and ability to obtain/maintain a security clearance.

Responsibilities

• Investigate edge-case behaviors and protocol signaling to reveal attack surfaces in proprietary telecom and embedded systems.
• Reverse-engineer 5G baseband firmware and NF binaries where source code is unavailable.
• Develop custom Python3 tools to automate protocol decoding, firmware unpacking, and analysis workflows.
• Develop and deploy custom stateful fuzzers for 3GPP protocols to identify crashes in the 5G Core.
• Use concolic and symbolic execution to map state machines and uncover logic flaws in session management and authentication flows.
• Create PoC exploits for vulnerabilities in components such as AMF, SMF, or UPF.
• Document findings clearly and translate technical protocol complexity into actionable reports.

Skills

5G protocol security

Reverse engineering

Python

C/C++

Disassembly tools

Hardware debugging

Tools

IDA Pro

Ghidra

Binary Ninja

JTAG/UART

Job description

Job Title: Senior Penetration Engineer (5G & Protocol Security)Job Category: EngineeringTime Type: Full timeMinimum Clearance Required to Start: NoneEmployee Type: RegularPercentage of Travel Required: Up to 10%Type of Travel: Continental US

The Opportunity

We are seeking a Senior Penetration Engineer with deep expertise in telecommunications security, 3GPP protocols, and advanced reverse engineering. This role is ideal for a specialist who thrives on technical ambiguity and enjoys probing the 5G stack for critical flaws. You’ll play a key role in evaluating the security and robustness of proprietary telecom systems—reverse-engineering "closed-box" binaries, developing stateful fuzzers, and uncovering vulnerabilities that contribute directly to national cybersecurity efforts.

Responsibilities

• Investigate edge‑case behaviors and low‑level protocol signaling to reveal attack surfaces in proprietary telecom and embedded systems.
• Apply advanced binary analysis to reverse-engineer proprietary 5G baseband firmware and Network Function (NF) binaries where source code is unavailable.
• Develop custom tools and scripts in Python3 to automate protocol decoding, firmware unpacking, and analysis workflows.
• Develop and deploy custom stateful fuzzers for 3GPP protocols (e.g., NGAP, HTTP/2, PFCP, GTP‑U) to identify crashes and stability issues in the 5G Core.
• Utilize concolic and symbolic execution (e.g., Angr, Manticore) to map complex state machines and uncover logic flaws in 5G session management and authentication flows.
• Create reliable Proof‑of‑Concept (PoC) exploits for discovered vulnerabilities in critical components such as AMF, SMF, or UPF.
• Document findings clearly and translate technical protocol complexity into actionable reports for security and engineering teams.

Qualifications

Required:

• 7+ years of professional experience in vulnerability research, protocol analysis, or reverse engineering.
• Deep understanding of 5G/4G architecture and 3GPP security standards.
• Detailed understanding of networking and telecom protocol stacks, including signaling, management and data plane components.
• Experience with Linux kernel internals or RTOS environments used in telecom hardware.
• Hands‑on experience with disassembly and decompilation tools (e.g., IDA Pro, Ghidra, Binary Ninja) and hardware‑assisted debugging.
• Must be a US Citizen, and able to obtain/maintain a security clearance.

Desired:

• An active TS//SCI clearance is highly desired.
• Experience in exploit development and vulnerability discovery in embedded or telecom environments.
• Proven track record of reconstructing proprietary binary protocols and analyzing "closed-box" telecom equipment.
• Mastery of C/C++ and high proficiency in Python for automation and tool development.
• Familiarity with radio access network (RAN) components and baseband security.
• Ability to build scalable fuzzing infrastructure and analysis tools in a team setting.
• Background in hardware‑level analysis, including firmware extraction and inspecting hardware state via JTAG or UART.

What You Can Expect

A culture of integrity.

At CACI, we place character and innovation at the center of everything we do. As a valued team member, you’ll be part of a high‑performing group dedicated to our customer’s missions and driven by a higher purpose – to ensure the safety of our nation.

An environment of trust.

CACI values the unique contributions that every employee brings to our company and our customers – every day. You’ll have the autonomy to take the time you need through a unique flexible time off benefit and have access to robust learning resources to make your ambitions a reality.

A focus on continuous growth.

Together, we will advance our nation’s most critical missions, build on our lengthy track record of business success, and find opportunities to break new ground — in your career and in our legacy.

Pay Range

There are a host of factors that can influence final salary including, but not limited to, geographic location, Federal Government contract labor categories and contract wage rates, relevant prior work experience, specific skills and competencies, education, and certifications. Our employees value the flexibility at CACI that allows them to balance quality work and their personal lives. We offer competitive compensation, benefits and learning and development opportunities. Our broad and competitive mix of benefits options is designed to support and protect employees and their families. At CACI, you will receive comprehensive benefits such as; healthcare, wellness, financial, retirement, family support, continuing education, and time off benefits.

The proposed salary range for this position is: $113,200 - $237,800.

Equal Opportunity Employer. All qualified applicants will receive consideration for employment without regard to race, color, religion, sex, pregnancy, sexual orientation, age, national origin, disability, status as a protected veteran, or any other protected characteristic.