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Public proof of conceptFix available

CVE-2026-43994

A public proof of concept exists; no exploitation attested.

  • Published2026-06-18
  • Fixed in4.10.0
  • WeaknessCWE-120

Am I affected?

With a domain, we read the version its public headers and pages expose. A distribution build can carry the fix under an older number.

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.

Timeline

dates in UTC
  1. 2026-06-1821:16CVE publishedNVD

Versions per branch

NVD
Coturn project coturn
BranchAffectedFixed in
4.10< 4.10.04.10.0

as publishedRanges as NVD and OSV publish them; a distribution’s build can be fixed under an older number.

Products declared by the CNA1 product

As GitHub_M, the CNA that assigned this CVE, declared them in the CVE record; versions as written.

  • coturn
    Affected
    • = < 4.10.0no fix stated

Source: the CNA record (CVE Program), © The MITRE Corporation,CVE Terms of UseCVE recordupdated 2026-06-18

Distribution builds and vendor advisories

Packages from OSV.dev and products from the vendors' CSAF advisories.

version not verifiedVersions not verified: read as OSV.dev and the vendors publish them, not checked against each vendor's release list.

Packages

  • coturnUbuntu:26.10all versions · no fixed version listed
  • coturnUbuntu:26.04:LTSall versions · no fixed version listed
  • coturnUbuntu:25.10all versions · no fixed version listed
  • coturnUbuntu:24.04:LTSall versions · no fixed version listed
  • coturnUbuntu:22.04:LTSall versions · no fixed version listed
  • coturnUbuntu:20.04:LTSall versions · no fixed version listed
  • coturnUbuntu:18.04:LTSall versions · no fixed version listed
  • coturnUbuntu:16.04:LTSall versions · no fixed version listed

4 more package ranges on OSV.dev

Full record on NVD

Fix

  1. Update Coturn project coturn to 4.10.0

Advisories and patches

Detection

Nuclei template
none so far
ProjectDiscovery
Exploit-DB
no entry
Exploit-DB
Proof of concept
Metasploit modules
none listed
Metasploit Framework

Sources

  • CISA-ADPSSVC decisionpoc2026-06-22
  • CNACVSS 3.18.1known since 2026-10-23
  • NVDCVSS 3.19.8read 2026-10-23
  • CNAweakness (CWE)CWE-120known since 2026-10-23
  • FIRST EPSSEPSS score0.7 %2026-11-08
  • OSVaffected packages—

Identifiers

Technical details

CVSS v3 Vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Published
2026-06-18
Last Modified
2026-06-26
NVD status
Analyzed

Frequently asked questions

What is CVE-2026-43994?

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.

Is CVE-2026-43994 actively exploited?

A proof-of-concept exploit exists for CVE-2026-43994, but active exploitation has not been confirmed at this time.

What is the CVSS score for CVE-2026-43994?

CVE-2026-43994 has a CVSS v3 base score of 9.8 (CRITICAL severity), with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.

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