Review reviewCritical

CVE-2026-43994

coturn

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 buffe...

CVSS: 9.8
EPSS: 0.45%
CISA KEV: Not listed
Published: 2026.06.19

PRIORITY ASSESSMENT

Review review

The CVSS severity warrants an early asset and exposure review.

Known exploitationNot established by KEV

Exploit probability0.45%

Technical severityCVSS 9.8

Vulnerability overview

Affected product and versions

Product: coturn
Affected versions: < 4.10.0
Fixed versions: 4.10.0

Recommended response sequence

Confirm exposure before applying a vendor-supported change.

Full remediation guide

1
Identify
Confirm that coturn and an affected version are present.
2
Prioritize
Combine exploitation signals with asset exposure and business criticality.
3
Remediate
Follow the vendor advisory or supported update path and preserve rollback options.
4
Verify
Recheck the version, service health, access paths, and relevant logs.

Technical data

CVSS vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CWE: CWE-120