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TI-2020-16083 Aliases CVE-2020-26262

Loopback bypass in Coturn

Priority LOW 35CWE-441Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Impact type
—
Confidentiality · integrity · availability
Low · Low · None
Fix status
Fixed

Attack profile from CVSS 3.1 · CNA. Fix status from CNA.

Summary

Coturn is free open source implementation of TURN and STUN Server. Coturn before version 4.5.2 by default does not allow peers to connect and relay packets to loopback addresses in the range of `127.x.x.x`. However, it was observed that when sending a `CONNECT` request with the `XOR-PEER-ADDRESS` value of `0.0.0.0`, a successful response was received and subsequently, `CONNECTIONBIND` also received a successful response. Coturn then is able to relay packets to the loopback interface. Additionally, when coturn is listening on IPv6, which is default, the loopback interface can also be reached by making use of either `[::1]` or `[::]` as the peer address. By using the address `0.0.0.0` as the peer address, a malicious user will be able to relay packets to the loopback interface, unless `--denied-peer-ip=0.0.0.0` (or similar) has been specified. Since the default configuration implies that loopback peers are not allowed, coturn administrators may choose to not set the `denied-peer-ip` setting. The issue patched in version 4.5.2. As a workaround the addresses in the address block `0.0.0.0/8`, `[::1]` and `[::]` should be denied by default unless `--allow-loopback-peers` has been specified.

Why it matters now

EPSS 0.01547 75th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed coturn (coturn): 4.5.2

SSVC decision points

Not available: CISA has not published SSVC decision points for this record.

Affected products

VendorProductAffected versionsFixed inStatusSource
coturncoturnbefore 4.5.24.5.2Patch availableCNA
  • coturn Vendorcoturn Affected before 4.5.2 Fixed in 4.5.2 Patch available CNA

CPE configurations NVD · 3

CPEVersionsRoleVendor
cpe:2.3:a:coturn_project:coturn:*:*:*:*:*:*:*:*before 4.5.2Vulnerablecoturn
cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:*32VulnerableFedoraproject
cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:*33VulnerableFedoraproject
  • cpe:2.3:a:coturn_project:coturn:*:*:*:*:*:*:*:* Versions before 4.5.2 Vulnerable ·coturn
  • cpe:2.3:o:fedoraproject:fedora:32:*:*:*:*:*:*:* Versions 32 Vulnerable ·Fedoraproject
  • cpe:2.3:o:fedoraproject:fedora:33:*:*:*:*:*:*:* Versions 33 Vulnerable ·Fedoraproject

Remediation

  • Fix · CNA coturn (coturn) Fixed in 4.5.2

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2020-26262

References

Exploit 1

Patch 1

Advisory 3

  • TI-2026-32037 Coturn: Stack buffer overflow in decode_oauth_token_gcm() CVSS 3.1CRITICAL 9.8
  • TI-2026-29348 Coturn: Misaligned Memory Access in coturn STUN Attribute Parser (Remote DoS on ARM64) CVSS 3.1HIGH 7.5
  • TI-2026-22006 Coturn: IPv4-mapped IPv6 (::ffff:0:0/96) bypasses denied-peer-ip ACL CVSS 3.1HIGH 7.2
  • TI-2026-38529 Coturn: SQL Injection in HTTPS Admin Panel Delete Operations CVSS 3.1HIGH 7.2
  • TI-2026-38531 Coturn: IPv4-mapped 127.0.0.1 bypasses default loopback peer protection CVSS 3.1HIGH 7.4
  • TI-2026-38530 Coturn: Arbitrary File Write via CLI psd Command CVSS 3.1MEDIUM 6.0
See all 13 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences