CVE-2026-102507: Sliver C2 Framework DOS Vulnerability

CVE-2026-102507 Overview

CVE-2026-102507 is a denial of service vulnerability in the Sliver command and control (C2) framework versions 1.7.7 and earlier. An unhandled panic in the operator gRPC handler allows an attacker who controls a compromised implant to crash the entire teamserver. The attacker sends a malformed or empty Download response, triggering an out-of-bounds slice access in the vendored Binject library's BinaryMagic function. The panic propagates through the operator gRPC interceptor chain and terminates the server process, disconnecting all connected operators.

Critical Impact
A single hostile implant session can terminate the Sliver teamserver process, disrupting active operations for every connected operator until the server is restarted.

Affected Products

Sliver C2 framework version 1.7.7
Sliver C2 framework versions prior to 1.7.7
Vendored Binject library BinaryMagic component within Sliver

Discovery Timeline

2026-09-29 - CVE-2026-102507 published to NVD
2026-09-30 - Last updated in NVD database

Technical Details for CVE-2026-102507

Vulnerability Analysis

Sliver is an open source adversary emulation and red team C2 framework. Operators interact with the teamserver over gRPC, and implants report back through implant-facing channels. The Download RPC returns file content retrieved from an implant. Before returning the content, the teamserver attempts to identify the file type by invoking the BinaryMagic function from the vendored Binject library.

BinaryMagic performs slice indexing on the response payload without validating that the buffer contains enough bytes. When an implant returns zero bytes or a payload of 1 to 3 bytes, the function indexes beyond the slice length. Go raises a runtime panic for the out-of-bounds access. The panic is not recovered by the operator gRPC interceptor chain, so the entire teamserver process exits.

This is an out-of-bounds read weakness classified as [CWE-125]. Because the crash affects the shared teamserver, every connected operator loses session state simultaneously.

Root Cause

The root cause is missing length validation in the BinaryMagic file-type detection routine combined with the absence of a recover() handler in the operator gRPC interceptor. The teamserver trusts implant-supplied response buffers to be well-formed and does not defensively bound-check them before slicing.

Attack Vector

Exploitation requires an attacker to control an implant already connected to a target teamserver. This models a scenario where a defender or third party has taken over a Sliver implant on a compromised host and turned it against the operator infrastructure. The attacker responds to a Download RPC with a zero-length or 1 to 3 byte payload, causing the teamserver process to panic and exit. No operator authentication is required, since the trigger travels the implant channel.

The vulnerability mechanism and a proof of concept are documented in the VulnCheck Security Advisory and the GitHub DoS Tool Repository.

Detection Methods for CVE-2026-102507

Indicators of Compromise

Unexpected termination of the Sliver teamserver process shortly after an implant returns a Download response.
Go runtime panic messages referencing BinaryMagic or slice bounds out of range in teamserver logs or stderr.
Multiple operator gRPC clients disconnecting simultaneously with connection reset errors.
Download RPC responses in traffic captures containing zero-length or 1 to 3 byte payloads.

Detection Strategies

Monitor teamserver stdout, stderr, and journal logs for panic: entries and stack frames referencing the Binject package.
Instrument the teamserver host with process monitoring to alert on unexpected exits of the sliver-server binary.
Track gRPC session churn on operator listeners, since a mass disconnect is a strong post-crash signal.

Monitoring Recommendations

Forward teamserver process telemetry, crash logs, and host EDR events into a central SIEM for correlation.
Alert on repeated teamserver restarts within short time windows, which suggests iterative crash attempts.
Baseline normal implant Download response sizes and flag anomalous sub-4-byte responses.

How to Mitigate CVE-2026-102507

Immediate Actions Required

Restrict the network exposure of Sliver teamservers and treat any implant callback host as untrusted.
Isolate operational teamservers from teamservers used for research or malware handling to limit blast radius.
Configure the teamserver to run under a process supervisor that restarts it after a crash while preserving logs for forensics.
Review implant sessions and terminate any that exhibit anomalous Download responses.

Patch Information

At the time of publication, no fixed version is referenced in the NVD entry. Track upstream Sliver releases newer than 1.7.7 for a fix that adds length validation in BinaryMagic and a recover() handler in the operator gRPC interceptor. Consult the VulnCheck Security Advisory for update guidance.

Workarounds

Run the teamserver under systemd or an equivalent supervisor with automatic restart on failure.
Apply a local patch that wraps the BinaryMagic call in a defer/recover() block and validates payload length before slicing.
Reduce the number of concurrent implants per teamserver so a crash affects fewer operations.
Segment operator gRPC listeners on separate teamserver instances per engagement.

bash

# Example systemd unit fragment to auto-restart the Sliver teamserver on crash
[Service]
ExecStart=/opt/sliver/sliver-server daemon
Restart=always
RestartSec=5s
StandardOutput=append:/var/log/sliver/teamserver.log
StandardError=append:/var/log/sliver/teamserver.err