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CVE-2026-4390 is a remotely triggerable heap use-after-free in TeamSpeak 3 Server up to and including 3.13.7, in connection state management around the process_resend_queue function. The issue occurs on the pre-authentication UDP protocol path during handshake processing when two clientinit messages are handled in a narrow timing window. The duplicate clientinit drives an error path that sends an error response packet requiring acknowledgement and then removes the client only from the endpoint-based lookup structure. The resend machinery tracks the resulting ResendingPacket in both the global resend queue and the client context ack window. Later, if the acknowledgement is withheld, process_resend_queue fails to resolve the client via the endpoint map and frees the ResendingPacket, but the corresponding pointer remains reachable from the client ack window via the client ID-based lookup path. When the delayed acknowledgement is subsequently processed, the server dereferences the stale pointer in acknowledgement handling, producing a heap use-after-free and crashing the ts3server process. Public analysis describes this as a reliable remote denial-of-service; although a virtual call exists on the affected path, no reliable code execution was demonstrated.
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1 valid exploit after Mallory filtered fakes, detection scripts, and README-only repos.
This repository contains three standalone Rust proof-of-concept exploits targeting TeamSpeak 3 Server 3.13.7: CVE-2026-4390, CVE-2026-4391, and CVE-2026-4392. The top-level README describes them as responsibly disclosed TeamSpeak server vulnerabilities and links to an advisory and blog post. Each CVE directory is a separate Cargo project with Cargo.toml, Cargo.lock, README.md, src/main.rs, and src/crypto.rs. Repository structure and purpose: - CVE-2026-4390: More complete exploit flow for a TeamSpeak 3 denial-of-service via use-after-free. Its main.rs implements both low-level and high-level TeamSpeak handshake logic over UDP, including init0/init1/init2/init3/init4 exchange, challenge solving, parsing of server responses, derivation of shared IV/MAC material, ECDSA identity generation, Ed25519 ephemeral key exchange, and encrypted command/ack packet construction. crypto.rs contains helper routines for TeamSpeak-related cryptographic operations: EAX encryption/decryption, Ed25519 shared secret handling, license parsing, SHA-based key derivation, proof-of-work/hashcash, and RSA challenge solving. This is the most feature-complete PoC in the repo. - CVE-2026-4391: Pre-auth DoS via heap-based buffer overflow. This project is smaller and uses a reduced crypto helper set. The exploit performs the TeamSpeak UDP handshake, sends a crafted clientinitiv with a fixed omega value, acknowledges initivexpand2 using fake encryption parameters, then sends a crafted clientek command with proof=ABCD to trigger an out-of-bounds write / crash. It does not attempt post-exploitation or code execution. - CVE-2026-4392: Pre-auth DoS via failing assertion. Similar structure to CVE-2026-4391, but it generates a normal omega from a P-256 identity key and then sends a clientek command with an empty proof field to trigger the vulnerable assertion path and crash the server. Capabilities: - All three binaries are remote network exploits using UDP against a TeamSpeak server, defaulting to port 9987. - They implement enough of the TeamSpeak protocol to reach vulnerable code paths rather than merely fuzzing blindly. - They solve the server’s RSA-based challenge and construct protocol-valid initialization packets. - CVE-2026-4390 additionally derives session material and sends encrypted high-level commands, making it the most protocol-aware PoC. - None of the samples provide persistence, shell access, credential theft, or arbitrary code execution; their practical effect is denial of service only. Notable protocol artifacts and observables: - UDP socket bound locally to 0.0.0.0:0 and connected to a user-supplied target. - Default target port 9987, consistent with TeamSpeak 3 server. - TeamSpeak init magic/header TS3INIT1 appears in crafted handshake packets. - High-level command strings include clientinitiv, clientek, and in CVE-2026-4390 also clientinit. - Fake EAX encryption uses hardcoded 16-byte key and nonce constants whose bytes resemble fragments of the Windows path c:\windows\system\firewall32.cpl split across key/nonce arrays. Assessment: This is a legitimate exploit repository, not a detector. The code is operational PoC-quality: it contains working packet builders, parsers, cryptographic helpers, and explicit crash-triggering logic, but no modular payload system or framework integration.
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