CVE-2026-68554Public exploit

Request tampering via post-HMAC STUN attributes

Published Aug 19, 2026 · Updated Aug 20, 2026

Message-integrity enforcement flaw in coturn before 4.15.0 allows on-path attackers to modify authenticated TURN requests via STUN attributes. In src/server/ns_turn_server.c, server-side parsers continue past MESSAGE-INTEGRITY even though check_stun_auth validates an HMAC over only the prefix up to that attribute; an attacker can extend the STUN length and recompute the unkeyed FINGERPRINT so trailing LIFETIME, XOR-PEER-ADDRESS, or ORIGIN attributes override the authenticated request. Exploitation requires an on-path position on plain UDP or TCP and can alter allocation lifetime, inject permissions, or satisfy the origin check, while TLS and DTLS prevent the in-transit rewrite.

CVSS severity2.3
Low
EPSS probability0.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Message-integrity enforcement flaw in coturn before 4.15.0 allows on-path attackers to modify authenticated TURN requests via STUN attributes. In src/server/ns_turn_server.c, server-side parsers continue past MESSAGE-INTEGRITY even though check_stun_auth validates an HMAC over only the prefix up to that attribute; an attacker can extend the STUN length and recompute the unkeyed FINGERPRINT so trailing LIFETIME, XOR-PEER-ADDRESS, or ORIGIN attributes override the authenticated request. Exploitation requires an on-path position on plain UDP or TCP and can alter allocation lifetime, inject permissions, or satisfy the origin check, while TLS and DTLS prevent the in-transit rewrite.

The record

CVE
CVE-2026-68554
Published
Aug 19, 2026
Updated
Aug 20, 2026
Vendor
coturn
Product
coturn
Classifications
CWE-924, CWE-345, T1557
Attack vector
adjacent
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 19, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 20, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=< 4.15.0

What conditions does exploitation require?

Attack vectoradjacent
Required privilegesunauthenticated

What is affected?

coturn · coturnversion=< 4.15.0

Published CVSS scores

2.3GitHub_MCVSS:4.0/AV:A/AC:L/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectoradjacent
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-924Improper Enforcement of Message Integrity During Transmission in a Communication Channel
CWE-345Insufficient Verification of Data Authenticity
T1557Adversary-in-the-Middle

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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