SIPSorcery: Malformed UDP packet on the RTP/ICE socket can remotely terminate a media session (DoS)

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

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.

Source published

14 Sep 2026 19:58:30 UTC

Source modified

15 Sep 2026 14:43:28 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

Source published

Sep 14, 2026, 7:58:30 PM (timezone not stated)

Source modified

Sep 15, 2026, 2:43:28 PM (timezone not stated)

Observed here

11 Nov 2026 14:00:55 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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EUVD CVSS 3.1 · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

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.

Source published

14 Sep 2026 20:16:47 UTC

Source modified

30 Sep 2026 17:51:56 UTC

Observed here

25 Oct 2026 13:17:28 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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CVSS 3.1 · [email protected] · Secondary · 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

### 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-RELAYED-ADDRESS` attribute of length 0–7 threw (`NullReferenceException` for length 0, `IndexOutOfRangeException`/`ArgumentOutOfRangeException` for 1–7). 2. **The UDP receive loop closed the channel on any exception.** The catch-all in `UdpReceiver.EndReceiveFrom` called `Close()`, tearing down the channel, instead of dropping the offending packet and continuing. This was systemic: any unhandled exception anywhere in the packet pipeline (STUN, RTP, RTCP, DTLS demux, SRTP, TURN) became a channel teardown. ### Fix - `UdpReceiver.EndReceiveFrom`: a non-socket exception now logs and drops the single packet and re-arms the receive loop (matching the existing `SIPUDPChannel` behaviour), instead of closing the channel. Genuine socket failures continue to be handled separately. - `RTPChannel.OnRTPPacketReceived`: requires a minimum packet length (`RTPHeader.MIN_HEADER_LEN`) before indexing the discriminator bytes. - STUN parsing: `ParseMessageAttributes` validates each attribute value length and skips malformed/truncated attributes; the XOR/address attribute constructors validate length defensively; `ParseSTUNMessage` no longer dereferences a null attribute list. Regression tests were added covering the 1-byte packet (channel stays open and remains usable), short/zero-length XOR address attributes (0–7 bytes), and truncated STUN messages. ### Workarounds None within the library short of upgrading. Restricting the RTP/ICE port to known peers at the network layer reduces exposure but does not eliminate it, since a negotiating peer can still trigger the condition. ### Credit Responsibly reported by Lokhesh Ujhoodha.

Source published

28 Jul 2026 17:01:19 UTC

Source modified

28 Jul 2026 17:26:50 UTC

Observed here

23 Oct 2026 16:01:25 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Publisher rating · HIGH