Home/CVE/Coturn is a free open source implementation of TURN and STUN Server. Versions prior to 4.10.0 contain a stack buffer ove
CVE

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 ove

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.

HIGH · CVSS 8.1 EPSS 0.0006
Schedule remediation
  • CVSS base score ≥ 7.0
Sigma rules0 YARA rules0
Look this up elsewhere - one-click external pivots
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▸ How to read a CVE - triage first, then detect and patch
This page is every public fact about CVE-2026-43994, cross-linked. Its job is to answer one question fast - does this need my attention now? - and then hand you the two things you do about it. Here is how an analyst reads it.
Triage: should I act now? Four signals, and they are not interchangeable:
CVSSseverity - how bad it is IF exploited, 0-10. A high CVSS alone is not urgency; a flaw can be a perfect 10 and never actually be attacked. EPSSprobability - a model’s estimate of the chance it is exploited in the next 30 days, 0-1. This is the “will it actually happen” signal. CISA KEVconfirmed - it is being exploited in the wild right now. The strongest signal on the page; KEV beats any score. Weaponisedavailability - public exploits / PoCs, and especially Metasploit modules rated Excellent / Great. Reliable, packaged exploit code means low-skill attackers can use it today.
How they combine: KEV, or a dependable Metasploit module, means patch now regardless of CVSS. High CVSS + low EPSS + no exploit is real but not an emergency - schedule it. Low CVSS but KEV-listed still gets patched now. The verdict above already weighed these for you; this is how it got there.
Then what - two workflows:
Detectwhen you cannot patch today, follow this CVE to the ATT&CK techniques it enables, then Build a SIEM detection (the green button) - author a rule, test it in Atomic, deploy it. That buys visibility while the patch waits. PatchAffected products / packages tell you if you are exposed; Fixed versions by distribution and Vendor advisories give the exact version that closes it.
Reading order for the panels below: verdict + badges, then Public exploits / Metasploit (is it weaponised), then ATT&CK techniques + Sigma / IDS rules (can I detect it), then Affected products / packages + Fixed versions (am I exposed, what patches it), then Threat actors / IOCs (who uses it), then Scoring & timeline / references (the evidence).
◆

ATT&CK techniques

3

Techniques this CVE enables - linked via CWECAPECATT&CK. High◆ = named directly in ATT&CK or Nuclei templates.

T1190 · Exploit Public-Facing Application T1190 · Exploit Public-Facing Application T1203 · Exploitation for Client Execution
▤ Build a SIEM detection for these techniques
▤

CAPEC attack patterns

12

Attack patterns this CVE enables - the bridge from weakness to ATT&CK technique.

CAPEC-CAPEC-10 · Buffer Overflow via Environment Variables CAPEC-CAPEC-100 · Overflow Buffers CAPEC-CAPEC-14 · Client-side Injection-induced Buffer Overflow CAPEC-CAPEC-24 · Filter Failure through Buffer Overflow CAPEC-CAPEC-42 · MIME Conversion CAPEC-CAPEC-44 · Overflow Binary Resource File CAPEC-CAPEC-45 · Buffer Overflow via Symbolic Links CAPEC-CAPEC-46 · Overflow Variables and Tags CAPEC-CAPEC-47 · Buffer Overflow via Parameter Expansion CAPEC-CAPEC-67 · String Format Overflow in syslog() CAPEC-CAPEC-8 · Buffer Overflow in an API Call CAPEC-CAPEC-9 · Buffer Overflow in Local Command-Line Utilities
⬡

Weakness Classification

CWE-120Buffer Copy without Checking Size of Input ('Classic Buffer Overflow')
▣

Scoring & Timeline

8.1
HIGH · CVSS v3.1 · [email protected]
View on NVD
Attack Vector
Network Adjacent Local Physical
Attack Complexity
Low High
Privileges Required
None Low High
User Interaction
None Required
Scope
Unchanged Changed
Confidentiality
None Low High
Integrity
None Low High
Availability
None Low High
Published to NVD18 Jun 2026 · 09:16 PM
CVSS VectorCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
🔗

References & Sources

2
Source URLs (vendor pages, mailing lists, write-ups). Exploit/PoC links are in their own section above to avoid duplication.
https://github.com/coturn/coturn/releases/tag/4.10.0
https://github.com/coturn/coturn/security/advisories/GHSA-74pg-rfh2-5qw5
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