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Coturn: Stack buffer overflow in decode_oauth_token_gcm()

Type: advisorySources: OSV

Coturn is a free open source implementation of TURN and STUN Server. Versions prior to 4.10.0 contain a stack buffer overflow in decode_oauth_token_gcm(). A uint16_t nonce_len field read from an attacker-supplied OAuth access token (0-65535) is passed directly to memcpy() as the copy length into a 256-byte stack buffer (oauth_encrypted_block.nonce[256]) without bounds checking. The overflow occurs before AES-GCM authentication is verified, the attacker does not need to know the OAuth key or produce a valid AES-GCM token. Up to 735 bytes of attacker-controlled data are written past the buffer, may corrupt adjacent stack data, including control-flow data depending on compiler, ABI, and mitigations. Requires --oauth mode (non-default). This may provide a plausible RCE primitive depending on exploit mitigations; because coturn is widely deployed for WebRTC TURN/STUN and --oauth is commonly recommended, impact can be broad. This issue has been fixed in version 4.10.0.

Products
Not specified
Affected versions
Not specified
Fixed versions
Not specified
CVEs
CVE-2026-43994
Confirmed fixed CVEs
Not specified
Updated in this feed
4 Nov 2026, 18:30 UTC · Revision 1

Source evidence

Coturn: Stack buffer overflow in decode_oauth_token_gcm()

core-osv · Original source

Published 18 Jun 2026, 19:44 UTC

Coturn is a free open source implementation of TURN and STUN Server. Versions prior to 4.10.0 contain a stack buffer overflow in decode_oauth_token_gcm(). A uint16_t nonce_len field read from an attacker-supplied OAuth access token (0-65535) is passed directly to memcpy() as the copy length into a 256-byte stack buffer (oauth_encrypted_block.nonce[256]) without bounds checking. The overflow occurs before AES-GCM authentication is verified, the attacker does not need to know the OAuth key or produce a valid AES-GCM token. Up to 735 bytes of attacker-controlled data are written past the buffer, may corrupt adjacent stack data, including control-flow data depending on compiler, ABI, and mitigations. Requires --oauth mode (non-default). This may provide a plausible RCE primitive depending on exploit mitigations; because coturn is widely deployed for WebRTC TURN/STUN and --oauth is commonly recommended, impact can be broad. This issue has been fixed in version 4.10.0.

osv:CVE-2026-43994
Complete source record
{
  "id": "d314f61d09d0bc7eb6377674aa94039903be95bc9bd293b69c500b1c717e02ab",
  "url": "https://osv.dev/vulnerability/CVE-2026-43994",
  "method": "structured",
  "payload": {
    "kind": "advisory",
    "title": "Coturn: Stack buffer overflow in decode_oauth_token_gcm()",
    "summary": "Coturn is a free open source implementation of TURN and STUN Server. Versions prior to 4.10.0 contain a stack buffer overflow in decode_oauth_token_gcm(). A uint16_t nonce_len field read from an attacker-supplied OAuth access token (0-65535) is passed directly to memcpy() as the copy length into a 256-byte stack buffer (oauth_encrypted_block.nonce[256]) without bounds checking. The overflow occurs before AES-GCM authentication is verified, the attacker does not need to know the OAuth key or produce a valid AES-GCM token. Up to 735 bytes of attacker-controlled data are written past the buffer, may corrupt adjacent stack data, including control-flow data depending on compiler, ABI, and mitigations. Requires --oauth mode (non-default). This may provide a plausible RCE primitive depending on exploit mitigations; because coturn is widely deployed for WebRTC TURN/STUN and --oauth is commonly recommended, impact can be broad. This issue has been fixed in version 4.10.0.",
    "evidence": "osv:CVE-2026-43994",
    "products": [],
    "severity": "high",
    "structured": {
      "id": "CVE-2026-43994",
      "aliases": [
        "CVE-2026-43994",
        "GHSA-74pg-rfh2-5qw5"
      ],
      "metrics": [
        {
          "type": "CVSS_V3",
          "score": "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"
        }
      ],
      "affected": [
        {
          "ranges": [
            {
              "repo": "https://github.com/coturn/coturn",
              "type": "GIT",
              "events": [
                {
                  "introduced": "0"
                },
                {
                  "fixed": "8e2c575229de615a3414bd9c81215c3b040471b4"
                }
              ],
              "database_specific": {
                "extracted_events": [
                  {
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "4.10.0"
                      }
                    ],
                    "source": "AFFECTED_FIELD",
                    "strategy": "StringRangeExpression"
                  },
                  {
                    "range": [
                      {
                        "fixed": "8e2c575229de615a3414bd9c81215c3b040471b4"
                      }
                    ],
                    "source": "REFERENCES_TAG",
                    "original_tag": "4.10.0"
                  },
                  {
                    "cpe": "cpe:2.3:a:coturn_project:coturn:*:*:*:*:*:*:*:*",
                    "range": [
                      {
                        "introduced": "0"
                      },
                      {
                        "fixed": "4.10.0"
                      }
                    ],
                    "source": "CPE_RANGE"
                  }
                ]
              }
            }
          ],
          "versions": [
            "docker/4.9.0-r0",
            "4.9.0",
            "docker/4.8.0-r1",
            "docker/4.8.0-r0",
            "4.8.0",
            "docker/4.7.0-r4",
            "docker/4.7.0-r3",
            "docker/4.7.0-r2",
            "docker/4.7.0-r1",
            "docker/4.7.0-r0",
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            "docker/4.6.3-r3",
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            "docker/4.6.2-r11",
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            "docker/4.6.2-r9",
            "docker/4.6.2-r8",
            "docker/4.6.2-r7",
            "docker/4.6.2-r6",
            "docker/4.6.2-r5",
            "docker/4.6.2-r4",
            "docker/4.6.2-r3",
            "docker/4.6.2-r2",
            "docker/4.6.2-r1",
            "docker/4.6.2-r0",
            "4.6.2",
            "docker/4.6.1-r3",
            "docker/4.6.1-r2",
            "docker/4.6.1-r1",
            "docker/4.6.1-r0",
            "docker/4.6.0-r1",
            "docker/4.6.0-r0",
            "4.6.0",
            "docker/4.5.2-r14",
            "docker/4.5.2-r13",
            "docker/4.5.2-r12",
            "docker/4.5.2-r11",
            "docker/4.5.2-r10",
            "docker/4.5.2-r9",
            "docker/4.5.2-r8",
            "docker/4.5.2-r7",
            "docker/4.5.2-r6",
            "docker/4.5.2-r0",
            "4.5.2",
            "4.5.1.3",
            "4.5.1.2",
            "4.5.1.1",
            "4.5.1.0",
            "4.5.0.7",
            "4.5.0.6",
            "4.5.0.5",
            "4.5.0.4",
            "4.5.0.3",
            "4.5.0.2",
            "4.5.0.1",
            "4.4.5.4",
            "4.4.5.3"
          ],
          "database_specific": {
            "source": "https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-43994.json"
          }
        }
      ],
      "modified": "2026-10-28T02:30:38.417586342Z",
      "provider": "osv",
      "references": [
        "https://github.com/coturn/coturn/releases/tag/4.10.0",
        "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43994.json",
        "https://github.com/coturn/coturn/security/advisories/GHSA-74pg-rfh2-5qw5",
        "https://nvd.nist.gov/vuln/detail/CVE-2026-43994"
      ],
      "provider_metadata": {
        "cwe_ids": [
          "CWE-120"
        ],
        "cna_assigner": "GitHub_M",
        "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/43xxx/CVE-2026-43994.json"
      }
    },
    "related_cves": [
      {
        "value": "CVE-2026-43994",
        "evidence": "/id"
      }
    ],
    "security_relevant": true,
    "severity_evidence": "/severity/0/score"
  },
  "source_id": "core-osv",
  "document_id": 505712,
  "published_at": "2026-06-18T19:44:46.575+00:00"
}