{"schemaVersion":3,"id":"CVE-2026-43994","aliases":["UBUNTU-CVE-2026-43994","DEBIAN-CVE-2026-43994"],"status":"published","duplicateOf":null,"title":null,"description":"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.","dates":{"published":"2026-06-18T19:44:46.575Z","modified":"2026-06-22T18:06:27.688Z","reserved":null,"kevAdded":[],"kevDue":[]},"cvss":{"headline":{"score":9.8,"severity":"critical","version":"3.1","versionLabel":"v3.1","source":"NVD","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","computed":false,"selection":"backend-summary"},"metrics":[{"version":"3.1","versionLabel":"v3.1","source":"CVE.org","score":8.1,"severity":"high","vector":"CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H","exploitability":null,"impact":null,"computed":false},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Ubuntu","score":9.8,"severity":"critical","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","exploitability":10,"impact":9.8,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"OSV · Debian","score":9.8,"severity":"critical","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","exploitability":10,"impact":9.8,"computed":true},{"version":"3.1","versionLabel":"v3.1","source":"NVD","score":9.8,"severity":"critical","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H","exploitability":null,"impact":null,"computed":false}]},"epss":{"probability":0.00675,"percentile":0.51552,"severity":"low","asOf":"2026-10-21T00:00:00.000Z","change":{"pp":0,"baselineDate":"2026-09-21T00:00:00.000Z","baselineScore":0.00675},"history":[{"date":"2026-09-14T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-15T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-16T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-17T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-18T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-19T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-20T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-21T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-21T00:00:00.000Z","score":0.00675,"percentile":0.51552}],"last30":[{"date":"2026-09-21T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-22T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-23T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-24T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-25T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-26T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-27T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-28T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-29T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-09-30T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-01T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-02T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-03T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-04T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-05T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-06T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-07T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-08T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-09T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-10T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-11T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-12T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-13T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-14T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-15T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-16T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-17T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-18T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-19T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-20T00:00:00.000Z","score":0.00675,"percentile":null},{"date":"2026-10-21T00:00:00.000Z","score":0.00675,"percentile":0.51552}]},"kev":{"state":"not-listed","entries":[],"listedCount":0,"totalCatalogs":3,"catalogs":[{"source":"cisa","label":"CISA","listed":false,"entry":null},{"source":"enisa","label":"ENISA","listed":false,"entry":null},{"source":"circl","label":"CIRCL","listed":false,"entry":null}]},"ransomware":{"state":"none-recorded","sources":[]},"exploits":[{"id":"GITHUB_COTURN_COTURN","name":"Coturn","source":"github","url":"https://github.com/coturn/coturn/security/advisories/GHSA-6g6j-r9rf-cm7p","maturity":"poc","reliabilityScore":0.3,"verified":false,"type":null,"platforms":[],"requiresAuth":null,"exploitdb":null,"metasploit":null}],"exploitCount":1,"weaknesses":[{"id":"CWE-120","name":"Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')","description":"The product copies an input buffer to an output buffer without verifying that the size of the input buffer is less than the size of the output buffer.","type":"weakness","status":"Incomplete","abstraction":"Base","likelihoodOfExploit":"High","url":"https://cwe.mitre.org/data/definitions/120.html"}],"affected":[{"vendor":"coturn_project","product":"coturn","name":"coturn","label":"coturn","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"< 4.10.0","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 4.10.0","eol":null,"hubHref":"/vendor/coturn_project/coturn"},{"vendor":"coturn","product":"coturn","name":"coturn","label":"coturn","ecosystem":null,"cpePart":"a","purl":null,"purlType":null,"versions":[{"text":"< 4.10.0","noFixRecorded":false,"fixedIn":null}],"versionsText":"< 4.10.0","eol":null,"hubHref":"/vendor/coturn/coturn"},{"vendor":"debian","product":"coturn","name":"coturn","label":"coturn","ecosystem":"Debian","cpePart":null,"purl":"pkg:deb/debian/coturn","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null},{"text":"< 4.12.0-1","noFixRecorded":false,"fixedIn":null}],"versionsText":"All versions (No fix recorded) | < 4.12.0-1","eol":null,"hubHref":null},{"vendor":"ubuntu","product":"coturn","name":"coturn","label":"coturn","ecosystem":"Ubuntu","cpePart":null,"purl":"pkg:deb/ubuntu/coturn","purlType":"deb","versions":[{"text":"All versions","noFixRecorded":true,"fixedIn":null}],"versionsText":"All versions (No fix recorded)","eol":null,"hubHref":null}],"affectedCount":4,"eol":{"hasEol":false,"count":0},"references":[{"url":"https://github.com/coturn/coturn/security/advisories/GHSA-74pg-rfh2-5qw5","label":"github.com/coturn/coturn/security/advisories/GHSA-74pg-rfh2-5qw5","hostname":"github.com","tags":["X Refsource CONFIRM","REPORT","Exploit","Mitigation","Vendor Advisory"]},{"url":"https://github.com/coturn/coturn/releases/tag/4.10.0","label":"github.com/coturn/coturn/releases/tag/4.10.0","hostname":"github.com","tags":["X Refsource MISC","REPORT","Release Notes"]},{"url":"https://ubuntu.com/security/CVE-2026-43994","label":"ubuntu.com/security/CVE-2026-43994","hostname":"ubuntu.com","tags":["REPORT"]},{"url":"https://www.cve.org/CVERecord?id=CVE-2026-43994","label":"www.cve.org/CVERecord?id=CVE-2026-43994","hostname":"www.cve.org","tags":["REPORT"]},{"url":"https://github.com/coturn/coturn/commit/5ca467e70915c033f371cd7a9742759c68f56363","label":"github.com/coturn/coturn/commit/5ca467e70915c033f371cd7a9742759c68f56363","hostname":"github.com","tags":["REPORT"]},{"url":"https://security-tracker.debian.org/tracker/CVE-2026-43994","label":"security-tracker.debian.org/tracker/CVE-2026-43994","hostname":"security-tracker.debian.org","tags":["Advisory"]}],"lineage":{"upstream":[],"downstream":["OPENSUSE-SU-2026:11617-1"],"duplicates":[],"related":["OPENSUSE-SU-2026:11617-1"]},"timeline":[{"kind":"published","date":"2026-06-18T19:44:46.575Z","label":"Published","detail":"Vulnerability first disclosed.","source":null},{"kind":"modified","date":"2026-06-22T18:06:27.688Z","label":"Last modified","detail":"Vulnerability information updated.","source":null}],"risk":{"score":70,"level":"high","profile":"Default","thresholds":{"critical":75,"high":50,"medium":25,"low":10}},"meta":{"dataAsOf":"2026-10-22T02:22:29.300Z","stale":false,"partial":false}}