SIPSorcery is a WebRTC, SIP, and VoIP library for C# and .NET. Prior to 10.0.9, RTPChannel.OnRTPPacketReceived and the STUNAttribute.ParseMessageAttributes, STUNXORAddressAttribute, and STUNAddressAttribute parsing path index untrusted bytes without sufficient length checks, while UdpReceiver.EndReceiveFrom closes the channel when those operations raise a non-socket exception. A remote party can send a single short RTP packet or malformed zero-to-seven-byte STUN address attribute to the shared RTP/ICE socket, including during ICE connectivity checks before DTLS or STUN MESSAGE-INTEGRITY verification, and terminate the active RTP or WebRTC media session. The attacker must reach or learn the advertised ephemeral RTP/ICE port, but no authentication or user interaction is required, and the impact is limited to availability. This issue is fixed in version 10.0.9.

Affected: NuGet: SIPSorcery

### Impact

A single malformed inbound UDP packet on the RTP/ICE socket can remotely terminate an active RTP or WebRTC media session. The packet receive handler indexes packet (and STUN attribute) bytes without sufficient length checks and throws, and the UDP receive loop converted any such exception into a channel `Close` rather than dropping the packet. One small, unauthenticated packet therefore ends the media session.

This is reachable during ICE connectivity checks — before the DTLS handshake and before any STUN `MESSAGE-INTEGRITY` verification. Because the RTP/ICE port is shared/advertised in the ICE candidates, a peer or on-path attacker can reach it (exposure is lower for a blind off-path attacker that must first learn the ephemeral port). Impact is availability only — no loss of confidentiality or integrity.

### Affected versions

NuGet package `SIPSorcery` `<= 10.0.8`.

### Patches

Fixed in `10.0.9`.

### Root cause

Two issues combine:

1. **Unchecked indexing of untrusted bytes.** - `RTPChannel.OnRTPPacketReceived` read `packet[1]` after only checking the packet was non-empty, so a 1-byte packet threw `IndexOutOfRangeException`. - `STUNAttribute.ParseMessageAttributes` passed a `null`/short value to the typed attribute parsers, and `STUNXORAddressAttribute` (and the non-XOR `STUNAddressAttribute`) then read `attributeValue[1]`, `AsSpan(2)` and `AsSpan(4)` with no length check. A STUN message carrying an `XOR-MAPPED-ADDRESS`, `XOR-PEER-ADDRESS` or `XOR-RE…