Vulnerability-Lookup

CVE-2026-123805 (GCVE-0-2026-123805)

Vulnerability from cvelistv5 – Published: 2026-11-09 19:57 – Updated: 2026-11-12 18:05

Title

SIPSorcery: Unbounded SCTP SACK gap/duplicate counts cause out-of-bounds read that kills the data-channel receive thread (DoS)

Summary

SIPSorcery is a WebRTC, SIP, and VoIP library for C# and .NET. Prior to 10.0.14, SctpSackChunk.ParseChunk reads the numGapAckBlocks and numDuplicateTSNs fields from an attacker-controlled SCTP SACK chunk without checking that the corresponding entries fit the declared chunk length. A negotiated WebRTC peer can send a checksum-valid malformed SACK chunk that drives the parser beyond the 262144-byte receive buffer. The resulting IndexOutOfRangeException bypasses the recoverable ApplicationException handler in RTCSctpTransport.DoReceive, causing the generic handler to exit the dedicated receive loop and permanently terminate the SCTP association and all data channels. This issue is fixed in 10.0.14.

Severity

7.5 (High)


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

SSVC

Exploitation: none Automatable: yes Technical Impact: partial

CISA Coordinator · CISA-ADP (v2.0.3)

Decision recorded 2026-11-12 16:37 UTC

CWE

CWE-125 - Out-of-bounds Read
CWE-755 - Improper Handling of Exceptional Conditions

Assigner

GitHub_M CNA under the mitre root

CNA scorecard C 72/100 over 7843 records in the last 180 days details

References

3 references

URL	Tags
https://github.com/sipsorcery-org/sipsorcery/secu…	x_refsource_CONFIRM
https://github.com/sipsorcery-org/sipsorcery/pull/1772	x_refsource_MISC
https://github.com/sipsorcery-org/sipsorcery/comm…	x_refsource_MISC

Impacted products

1 product

Vendor	Product	Version	CPE status
sipsorcery-org	sipsorcery	Affected: < 10.0.14	guessed

Show details on NVD website

JSON

To clipboard

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FKIE_CVE-2026-123805

Vulnerability from fkie_nvd - Published: 2026-11-09 20:18 - Updated: 2026-11-12 19:16

Severity

7.5 (High) - CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Summary

References

	URL	Tags
	security-advisories@github.com	https://github.com/sipsorcery-org/sipsorcery/commit/a2466550bb2a28821c73fb1961bc33dcc467f8cf
	security-advisories@github.com	https://github.com/sipsorcery-org/sipsorcery/pull/1772
	security-advisories@github.com	https://github.com/sipsorcery-org/sipsorcery/security/advisories/GHSA-jwjp-4649-v8jp

Impacted products

	Vendor	Product	Version

JSON

To clipboard

{
  "affected": [
    {
      "affectedData": [
        {
          "product": "sipsorcery",
          "vendor": "sipsorcery-org",
          "versions": [
            {
              "status": "affected",
              "version": "\u003c 10.0.14"
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GHSA-JWJP-4649-V8JP

Vulnerability from github – Published: 2026-08-12 19:30 – Updated: 2026-11-09 19:57

Summary

SIPSorcery vulnerable to Denial of Service via out-of-bounds read in SCTP SACK chunk parsing

Details

Summary

SctpSackChunk.ParseChunk reads the numGapAckBlocks and numDuplicateTSNs fields (each up to 65535) directly from an attacker-controlled SCTP SACK chunk and loops that many times reading 4 bytes per iteration, with no validation of the counts against the chunk length or the receive buffer. A single crafted SACK chunk from a negotiated WebRTC peer forces reads past the end of the 262144-byte receive buffer, raising IndexOutOfRangeException, which is not caught by the recoverable handler and terminates the dedicated SCTP receive thread — permanently killing the SCTP association and all data channels.

Root Cause

src/SIPSorcery/net/SCTP/Chunks/SctpSackChunk.cs: - ushort numGapAckBlocks = NetConvert.ParseUInt16(buffer, startPosn + 8); (:141) - ushort numDuplicateTSNs = NetConvert.ParseUInt16(buffer, startPosn + 10); (:142) - gap-ack loop (:146) and duplicate-TSN loop (:154) index the buffer via NetConvert.ParseUInt16/32 (buffer[posn], no bounds check — sys/Net/NetConvert.cs:30,41). SctpPacket.ParseChunks (SctpPacket.cs:195-203) only validates chunkLength >= 4 and posn+chunkLength <= length; the counts inside the value are never checked. RTCSctpTransport.DoReceive calls SctpPacket.Parse(recvBuffer, 0, bytesRead) on a reused recvBuffer = new byte[262144].

Impact

IndexOutOfRangeException is a SystemException, not ApplicationException, so the recoverable catch (ApplicationException) { … continue; } at RTCSctpTransport.cs:345 is skipped and control falls to the generic catch (Exception) { … break; } at :356. The break exits the receive loop, DoReceive returns, and the dedicated _receiveThread = new Thread(DoReceive) (:173, started once) exits with no restart → the SCTP association and every data channel are permanently dead (denial of service).

Proof of Concept

A negotiated WebRTC peer (post-DTLS) sends a checksum-valid SCTP packet: 12-byte common header + a SACK chunk (type 3) with chunkLength=16, numGapAckBlocks=0xFFFF, numDuplicateTSNs=0xFFFF. CRC32C is attacker-computable. The gap-ack loop reaches buffer[262144] on a 262144-byte array (valid indices 0..262143) → IndexOutOfRangeException.

Attack Chain

Entry: post-DTLS negotiated peer sends a checksum-valid SCTP packet with a SACK chunk (chunkLength=16, numGapAckBlocks=0xFFFF). Guard: VerifyChecksum (CRC32C). Bypass: CRC32C is computable by the sender.
Processing: DoReceive (RTCSctpTransport.cs:286) reads into reused recvBuffer (262144 bytes, :280) → SctpPacket.Parse(recvBuffer, 0, bytesRead) (:302) → ParseChunks → SACK dispatch (SctpChunk.Parse :340-341) → SctpSackChunk.ParseChunk. Guard: ParseChunks checks only chunkLength>=4 and posn+chunkLength<=length (SctpPacket.cs:195-203). Bypass: chunkLength=16 is well-formed; the counts are never validated.
Sink: gap-ack loop (SctpSackChunk.cs:146) calls NetConvert.ParseUInt16(buffer, reportPosn) with reportPosn starting at startPosn(16)+FIXED_PARAMETERS(12)=28, climbing +4 each iteration. Guard: none on the count. Bypass: NetConvert.ParseUInt16 (NetConvert.cs:30) indexes buffer[posn] unchecked.
Impact: at iteration 65529, reportPosn = 28 + 65529*4 = 262144 → buffer[262144] → IndexOutOfRangeException → generic catch at RTCSctpTransport.cs:356 → break → receive thread exits, no restart → association permanently dead.

Bypass Evidence

Unchecked counts at SctpSackChunk.cs:141-142; loops at :146,:154.
NetConvert.ParseUInt16 unchecked indexing (NetConvert.cs:30).
ParseChunks validates only chunkLength (SctpPacket.cs:195-203).
OOB math: 28 + 65535*4 = 262168 > 262144; buffer is 262144 (DEFAULT_ADVERTISED_RECEIVE_WINDOW, SctpAssociation.cs:62). numGapAckBlocks alone suffices — the dup-TSN loop is not needed.
DoReceive catch split: recoverable catch(ApplicationException) at :345 (continue) vs generic catch(Exception) at :356 (break); _receiveThread started once at :176.

Affected Versions

nuget:SIPSorcery <= 10.0.13 (verified present on release tag v10.0.13 and HEAD da944543).

Dedup

NOT a duplicate of GHSA-qmvg-569h-hqrh — that fix (fe5a1fa) touched only SctpPacket.cs (the chunk-cursor zero-length infinite loop, CWE-835). This is a distinct out-of-bounds read (CWE-125) in SctpSackChunk count loops, untouched by that fix.

Suggested Fix

Validate startPosn + FIXED_PARAMETERS_LENGTH + numGapAckBlocks*4 + numDuplicateTSNs*4 <= posn + chunkLen before the loops, and/or make NetConvert.Parse* bounds-checked, and/or treat IndexOutOfRangeException/ArgumentException as recoverable in DoReceive.

Reported by zx (Jace) — GitHub: @manus-use

Severity

7.5 (High)


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

Show details on source website

JSON

To clipboard

{
  "affected": [
    {
      "database_specific": {
        "last_known_affected_version_range": "\u003c= 10.0.13"
      },
      "package": {
        "ecosystem": "NuGet",
        "name": "SIPSorcery"
      },
      "ranges": [
        {
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            {
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            }
          ],
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        }
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  "database_specific": {
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      "CWE-125",
      "CWE-755"
    ],
    "github_reviewed": true,
    "github_reviewed_at": "2026-08-12T19:30:43Z",
    "nvd_published_at": null,
    "severity": "HIGH"
  },
  "details": "## Summary\n`SctpSackChunk.ParseChunk` reads the `numGapAckBlocks` and `numDuplicateTSNs` fields (each up to 65535) directly from an attacker-controlled SCTP SACK chunk and loops that many times reading 4 bytes per iteration, with no validation of the counts against the chunk length or the receive buffer. A single crafted SACK chunk from a negotiated WebRTC peer forces reads past the end of the 262144-byte receive buffer, raising `IndexOutOfRangeException`, which is not caught by the recoverable handler and terminates the dedicated SCTP receive thread \u2014 permanently killing the SCTP association and all data channels.\n\n## Root Cause\n`src/SIPSorcery/net/SCTP/Chunks/SctpSackChunk.cs`:\n- `ushort numGapAckBlocks = NetConvert.ParseUInt16(buffer, startPosn + 8);` (:141)\n- `ushort numDuplicateTSNs = NetConvert.ParseUInt16(buffer, startPosn + 10);` (:142)\n- gap-ack loop (:146) and duplicate-TSN loop (:154) index the buffer via `NetConvert.ParseUInt16/32` (`buffer[posn]`, no bounds check \u2014 `sys/Net/NetConvert.cs:30,41`).\n`SctpPacket.ParseChunks` (SctpPacket.cs:195-203) only validates `chunkLength \u003e= 4` and `posn+chunkLength \u003c= length`; the counts inside the value are never checked. `RTCSctpTransport.DoReceive` calls `SctpPacket.Parse(recvBuffer, 0, bytesRead)` on a reused `recvBuffer = new byte[262144]`.\n\n## Impact\n`IndexOutOfRangeException` is a `SystemException`, not `ApplicationException`, so the recoverable `catch (ApplicationException) { \u2026 continue; }` at RTCSctpTransport.cs:345 is skipped and control falls to the generic `catch (Exception) { \u2026 break; }` at :356. The `break` exits the receive loop, `DoReceive` returns, and the dedicated `_receiveThread = new Thread(DoReceive)` (:173, started once) exits with no restart \u2192 the SCTP association and every data channel are permanently dead (denial of service).\n\n## Proof of Concept\nA negotiated WebRTC peer (post-DTLS) sends a checksum-valid SCTP packet: 12-byte common header + a SACK chunk (type 3) with `chunkLength=16`, `numGapAckBlocks=0xFFFF`, `numDuplicateTSNs=0xFFFF`. CRC32C is attacker-computable. The gap-ack loop reaches `buffer[262144]` on a 262144-byte array (valid indices 0..262143) \u2192 `IndexOutOfRangeException`.\n\n## Attack Chain\n1. Entry: post-DTLS negotiated peer sends a checksum-valid SCTP packet with a SACK chunk (`chunkLength=16`, `numGapAckBlocks=0xFFFF`). Guard: `VerifyChecksum` (CRC32C). Bypass: CRC32C is computable by the sender.\n2. Processing: `DoReceive` (RTCSctpTransport.cs:286) reads into reused `recvBuffer` (262144 bytes, :280) \u2192 `SctpPacket.Parse(recvBuffer, 0, bytesRead)` (:302) \u2192 `ParseChunks` \u2192 SACK dispatch (`SctpChunk.Parse` :340-341) \u2192 `SctpSackChunk.ParseChunk`. Guard: `ParseChunks` checks only `chunkLength\u003e=4` and `posn+chunkLength\u003c=length` (SctpPacket.cs:195-203). Bypass: `chunkLength=16` is well-formed; the counts are never validated.\n3. Sink: gap-ack loop (SctpSackChunk.cs:146) calls `NetConvert.ParseUInt16(buffer, reportPosn)` with `reportPosn` starting at `startPosn(16)+FIXED_PARAMETERS(12)=28`, climbing `+4` each iteration. Guard: none on the count. Bypass: `NetConvert.ParseUInt16` (NetConvert.cs:30) indexes `buffer[posn]` unchecked.\n4. Impact: at iteration 65529, `reportPosn = 28 + 65529*4 = 262144` \u2192 `buffer[262144]` \u2192 `IndexOutOfRangeException` \u2192 generic `catch` at RTCSctpTransport.cs:356 \u2192 `break` \u2192 receive thread exits, no restart \u2192 association permanently dead.\n\n## Bypass Evidence\n- Unchecked counts at SctpSackChunk.cs:141-142; loops at :146,:154.\n- `NetConvert.ParseUInt16` unchecked indexing (NetConvert.cs:30).\n- `ParseChunks` validates only `chunkLength` (SctpPacket.cs:195-203).\n- OOB math: `28 + 65535*4 = 262168 \u003e 262144`; buffer is 262144 (`DEFAULT_ADVERTISED_RECEIVE_WINDOW`, SctpAssociation.cs:62). `numGapAckBlocks` alone suffices \u2014 the dup-TSN loop is not needed.\n- `DoReceive` catch split: recoverable `catch(ApplicationException)` at :345 (`continue`) vs generic `catch(Exception)` at :356 (`break`); `_receiveThread` started once at :176.\n\n## Affected Versions\n`nuget:SIPSorcery \u003c= 10.0.13` (verified present on release tag v10.0.13 and HEAD da944543).\n\n## Dedup\nNOT a duplicate of GHSA-qmvg-569h-hqrh \u2014 that fix (`fe5a1fa`) touched only `SctpPacket.cs` (the chunk-cursor zero-length infinite loop, CWE-835). This is a distinct out-of-bounds read (CWE-125) in `SctpSackChunk` count loops, untouched by that fix.\n\n## Suggested Fix\nValidate `startPosn + FIXED_PARAMETERS_LENGTH + numGapAckBlocks*4 + numDuplicateTSNs*4 \u003c= posn + chunkLen` before the loops, and/or make `NetConvert.Parse*` bounds-checked, and/or treat `IndexOutOfRangeException`/`ArgumentException` as recoverable in `DoReceive`.\n\n---\nReported by **zx (Jace)** \u2014 GitHub: @manus-use",
  "id": "GHSA-jwjp-4649-v8jp",
  "modified": "2026-11-09T19:57:41Z",
  "published": "2026-08-12T19:30:43Z",
  "references": [
    {
      "type": "WEB",
      "url": "https://github.com/sipsorcery-org/sipsorcery/security/advisories/GHSA-jwjp-4649-v8jp"
    },
    {
      "type": "WEB",
      "url": "https://github.com/sipsorcery-org/sipsorcery/commit/a2466550bb2a28821c73fb1961bc33dcc467f8cf"
    },
    {
      "type": "PACKAGE",
      "url": "https://github.com/sipsorcery-org/sipsorcery"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ],
  "summary": "SIPSorcery vulnerable to Denial of Service via out-of-bounds read in SCTP SACK chunk parsing"
}

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CVE-2026-123805 (GCVE-0-2026-123805)

FKIE_CVE-2026-123805

GHSA-JWJP-4649-V8JP

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