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CVE-2026-27624

Coturn: IPv4-mapped IPv6 (::ffff:0:0/96) bypasses denied-peer-ip ACL

7.2 HighFix available

Coturn is a free open source implementation of TURN and STUN Server. Coturn is commonly configured to block loopback and internal ranges using "denied-peer-ip" and/or default loopback restrictions. CVE-2020-26262 addressed bypasses involving "0.0.0.0", "[::1]" and "[::]", but IPv4-mapped IPv6 is not covered. When sending a "CreatePermission" or "ChannelBind" request with the "XOR-PEER-ADDRESS" value of "::ffff:127.0.0.1", a successful response is received, even though "127.0.0.0/8" is blocked via "denied-peer-ip". The root cause is that, prior to the updated fix implemented in version 4.9.0, three functions in "src/client/ns_turn_ioaddr.c" do not check "IN6_IS_ADDR_V4MAPPED". "ioa_addr_is_loopback()" checks "127.x.x.x" (AF_INET) and "::1" (AF_INET6), but not "::ffff:127.0.0.1." "ioa_addr_is_zero()" checks "0.0.0.0" and "::", but not "::ffff:0.0.0.0." "addr_less_eq()" used by "ioa_addr_in_range()" for "denied-peer-ip" matching: when the range is AF_INET and the peer is AF_INET6, the comparison returns 0 without extracting the embedded IPv4. Version 4.9.0 contains an updated fix to address the bypass of the fix for CVE-2020-26262.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
Low
Integrity
Low
Availability
None

Exploit likelihood

0.34%Up 0.3 points since Feb 25, 2026
90%50%10%1%

What each source reports

CVE List Score used 7.2

Coturn: IPv4-mapped IPv6 (::ffff:0:0/96) bypasses denied-peer-ip ACL

Coturn is a free open source implementation of TURN and STUN Server. Coturn is commonly configured to block loopback and internal ranges using "denied-peer-ip" and/or default loopback restrictions. CVE-2020-26262 addressed bypasses involving "0.0.0.0", "[::1]" and "[::]", but IPv4-mapped IPv6 is not covered. When sending a "CreatePermission" or "ChannelBind" request with the "XOR-PEER-ADDRESS" value of "::ffff:127.0.0.1", a successful response is received, even though "127.0.0.0/8" is blocked via "denied-peer-ip". The root cause is that, prior to the updated fix implemented in version 4.9.0, three functions in "src/client/ns_turn_ioaddr.c" do not check "IN6_IS_ADDR_V4MAPPED". "ioa_addr_is_loopback()" checks "127.x.x.x" (AF_INET) and "::1" (AF_INET6), but not "::ffff:127.0.0.1." "ioa_addr_is_zero()" checks "0.0.0.0" and "::", but not "::ffff:0.0.0.0." "addr_less_eq()" used by "ioa_addr_in_range()" for "denied-peer-ip" matching: when the range is AF_INET and the peer is AF_INET6, the comparison returns 0 without extracting the embedded IPv4. Version 4.9.0 contains an updated fix to address the bypass of the fix for CVE-2020-26262.

Record
CVE-2026-27624
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Weakness
CWE-284, CWE-441
Updated
2026-11-02
EUVDEUVD-2026-8620 7.2

Coturn is a free open source implementation of TURN and STUN Server. Coturn is commonly configured to block loopback and internal ranges using "denied-peer-ip" and/or default loopback restrictions. CVE-2020-26262 addressed bypasses involving "0.0.0.0", "[::1]" and "[::]", but IPv4-mapped IPv6 is not covered. When sending a "CreatePermission" or "ChannelBind" request with the "XOR-PEER-ADDRESS" value of "::ffff:127.0.0.1", a successful response is received, even though "127.0.0.0/8" is blocked via "denied-peer-ip". The root cause is that, prior to the updated fix implemented in version 4.9.0, three functions in "src/client/ns_turn_ioaddr.c" do not check "IN6_IS_ADDR_V4MAPPED". "ioa_addr_is_loopback()" checks "127.x.x.x" (AF_INET) and "::1" (AF_INET6), but not "::ffff:127.0.0.1." "ioa_addr_is_zero()" checks "0.0.0.0" and "::", but not "::ffff:0.0.0.0." "addr_less_eq()" used by "ioa_addr_in_range()" for "denied-peer-ip" matching: when the range is AF_INET and the peer is AF_INET6, the comparison returns 0 without extracting the embedded IPv4. Version 4.9.0 contains an updated fix to address the bypass of the fix for CVE-2020-26262.

Record
EUVD-2026-8620
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Updated
2026-11-02
NVD 7.2

Coturn is a free open source implementation of TURN and STUN Server. Coturn is commonly configured to block loopback and internal ranges using "denied-peer-ip" and/or default loopback restrictions. CVE-2020-26262 addressed bypasses involving "0.0.0.0", "[::1]" and "[::]", but IPv4-mapped IPv6 is not covered. When sending a "CreatePermission" or "ChannelBind" request with the "XOR-PEER-ADDRESS" value of "::ffff:127.0.0.1", a successful response is received, even though "127.0.0.0/8" is blocked via "denied-peer-ip". The root cause is that, prior to the updated fix implemented in version 4.9.0, three functions in "src/client/ns_turn_ioaddr.c" do not check "IN6_IS_ADDR_V4MAPPED". "ioa_addr_is_loopback()" checks "127.x.x.x" (AF_INET) and "::1" (AF_INET6), but not "::ffff:127.0.0.1." "ioa_addr_is_zero()" checks "0.0.0.0" and "::", but not "::ffff:0.0.0.0." "addr_less_eq()" used by "ioa_addr_in_range()" for "denied-peer-ip" matching: when the range is AF_INET and the peer is AF_INET6, the comparison returns 0 without extracting the embedded IPv4. Version 4.9.0 contains an updated fix to address the bypass of the fix for CVE-2020-26262.

Record
CVE-2026-27624
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Weakness
CWE-284, CWE-441
Updated
2026-11-02
OSVALPINE-CVE-2026-27624 6.5

Coturn is a free open source implementation of TURN and STUN Server. Coturn is commonly configured to block loopback and internal ranges using "denied-peer-ip" and/or default loopback restrictions. CVE-2020-26262 addressed bypasses involving "0.0.0.0", "[::1]" and "[::]", but IPv4-mapped IPv6 is not covered. When sending a "CreatePermission" or "ChannelBind" request with the "XOR-PEER-ADDRESS" value of "::ffff:127.0.0.1", a successful response is received, even though "127.0.0.0/8" is blocked via "denied-peer-ip". The root cause is that, prior to the updated fix implemented in version 4.9.0, three functions in "src/client/ns_turn_ioaddr.c" do not check "IN6_IS_ADDR_V4MAPPED". "ioa_addr_is_loopback()" checks "127.x.x.x" (AF_INET) and "::1" (AF_INET6), but not "::ffff:127.0.0.1." "ioa_addr_is_zero()" checks "0.0.0.0" and "::", but not "::ffff:0.0.0.0." "addr_less_eq()" used by "ioa_addr_in_range()" for "denied-peer-ip" matching: when the range is AF_INET and the peer is AF_INET6, the comparison returns 0 without extracting the embedded IPv4. Version 4.9.0 contains an updated fix to address the bypass of the fix for CVE-2020-26262.

Record
ALPINE-CVE-2026-27624
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Updated
2026-11-03
OSV 7.2

Coturn: IPv4-mapped IPv6 (::ffff:0:0/96) bypasses denied-peer-ip ACL

Coturn is a free open source implementation of TURN and STUN Server. Coturn is commonly configured to block loopback and internal ranges using "denied-peer-ip" and/or default loopback restrictions. CVE-2020-26262 addressed bypasses involving "0.0.0.0", "[::1]" and "[::]", but IPv4-mapped IPv6 is not covered. When sending a "CreatePermission" or "ChannelBind" request with the "XOR-PEER-ADDRESS" value of "::ffff:127.0.0.1", a successful response is received, even though "127.0.0.0/8" is blocked via "denied-peer-ip". The root cause is that, prior to the updated fix implemented in version 4.9.0, three functions in "src/client/ns_turn_ioaddr.c" do not check "IN6_IS_ADDR_V4MAPPED". "ioa_addr_is_loopback()" checks "127.x.x.x" (AF_INET) and "::1" (AF_INET6), but not "::ffff:127.0.0.1." "ioa_addr_is_zero()" checks "0.0.0.0" and "::", but not "::ffff:0.0.0.0." "addr_less_eq()" used by "ioa_addr_in_range()" for "denied-peer-ip" matching: when the range is AF_INET and the peer is AF_INET6, the comparison returns 0 without extracting the embedded IPv4. Version 4.9.0 contains an updated fix to address the bypass of the fix for CVE-2020-26262.

Record
CVE-2026-27624
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
Weakness
CWE-284, CWE-441
Updated
2026-11-02
OSVDEBIAN-CVE-2026-27624 6.5

Coturn is a free open source implementation of TURN and STUN Server. Coturn is commonly configured to block loopback and internal ranges using "denied-peer-ip" and/or default loopback restrictions. CVE-2020-26262 addressed bypasses involving "0.0.0.0", "[::1]" and "[::]", but IPv4-mapped IPv6 is not covered. When sending a "CreatePermission" or "ChannelBind" request with the "XOR-PEER-ADDRESS" value of "::ffff:127.0.0.1", a successful response is received, even though "127.0.0.0/8" is blocked via "denied-peer-ip". The root cause is that, prior to the updated fix implemented in version 4.9.0, three functions in "src/client/ns_turn_ioaddr.c" do not check "IN6_IS_ADDR_V4MAPPED". "ioa_addr_is_loopback()" checks "127.x.x.x" (AF_INET) and "::1" (AF_INET6), but not "::ffff:127.0.0.1." "ioa_addr_is_zero()" checks "0.0.0.0" and "::", but not "::ffff:0.0.0.0." "addr_less_eq()" used by "ioa_addr_in_range()" for "denied-peer-ip" matching: when the range is AF_INET and the peer is AF_INET6, the comparison returns 0 without extracting the embedded IPv4. Version 4.9.0 contains an updated fix to address the bypass of the fix for CVE-2020-26262.

Record
DEBIAN-CVE-2026-27624
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Updated
2026-11-02
Show 4 moreShow less
OSVUBUNTU-CVE-2026-27624 7.2

Coturn is a free open source implementation of TURN and STUN Server. Coturn is commonly configured to block loopback and internal ranges using "denied-peer-ip" and/or default loopback restrictions. CVE-2020-26262 addressed bypasses involving "0.0.0.0", "[::1]" and "[::]", but IPv4-mapped IPv6 is not covered. When sending a "CreatePermission" or "ChannelBind" request with the "XOR-PEER-ADDRESS" value of "::ffff:127.0.0.1", a successful response is received, even though "127.0.0.0/8" is blocked via "denied-peer-ip". The root cause is that, prior to the updated fix implemented in version 4.9.0, three functions in "src/client/ns_turn_ioaddr.c" do not check "IN6_IS_ADDR_V4MAPPED". "ioa_addr_is_loopback()" checks "127.x.x.x" (AF_INET) and "::1" (AF_INET6), but not "::ffff:127.0.0.1." "ioa_addr_is_zero()" checks "0.0.0.0" and "::", but not "::ffff:0.0.0.0." "addr_less_eq()" used by "ioa_addr_in_range()" for "denied-peer-ip" matching: when the range is AF_INET and the peer is AF_INET6, the comparison returns 0 without extracting the embedded IPv4. Version 4.9.0 contains an updated fix to address the bypass of the fix for CVE-2020-26262.

Record
UBUNTU-CVE-2026-27624
CVSS 3.1
7.2 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:L/I:L/A:N
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:L/A:N
Updated
2026-11-02
OSVMGASA-2026-0051 No score

Updated coturn packages fix security vulnerability

IPv4-mapped IPv6 (::ffff:0:0/96) bypasses denied-peer-ip ACL. (CVE-2026-27624)

Record
MGASA-2026-0051
Updated
2026-11-02
OSVopenSUSE-SU-2026:10375-1 No score

coturn-4.9.0-1.1 on GA media

These are all security issues fixed in the coturn-4.9.0-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2026:10375-1
Updated
2026-11-02
OSVopenSUSE-SU-2026:21184-1 No score

Security update for coturn

This update for coturn fixes the following issues:

Changes in coturn:

  • Update to version 4.14.0 New

    • No more dependency on prometheus-client-c
    • HTTPS support for prometheus client (optional)
    • TLS support for redis - now compatible with managed redis (optional).
    • Rate limiting "401 Unauthorized" responses - reduces reflection attacks off the coturn server. This is an experimental feature - not fully tested on production scale deployment and massive DDoS attacks. New prometheus counters should help shed some light on real life behavior and performance. The feature is off by default. What's Changed
    • validate hmackey length in sqlite_get_user_key before hex decode.
    • Add out-of-tree patch to restore deprecated OpenSSL 1.1.1.
    • Add optional TLS transport for Redis connections.
    • Fix relay threads override.
    • Flush prometheus hot-path counters once per second to kill lock contention.
    • fix signed-char index out-of-bounds read in base64_decode.
    • Build Prometheus exporter from vendored local sources.
    • Prom https.
    • Fix realm quota data race and warnings.
    • Add per-source rate-limiting of UDP 401 Unauthorized responses

  • Update to version 4.13.1

    • null-terminate server_name in stun_is_challenge_response_str.
    • Canonicalize all IPv4-in-IPv6 encodings before peer-IP checks.
    • Auto-deny coturn's own database backend endpoints as relay peers.
    • Deny link-local / ULA / site-local relay peers by default.

  • Update to version 4.13.0

    • Wrap atomic everywhere.
    • Fix sendmmsg stride bug in multiplex-peer UDP batch flush.
    • Reap TURN permissions/channels via a per-thread sweep instead of per-object timers.
    • Add --udp-sendmmsg-log to observe egress sendmmsg/UDP-GSO batching.
    • Expose recvmmsg/sendmmsg UDP batch sizes as Prometheus metrics
    • Restrict recvmmsg fast path to shared fan-in sockets (make --udp-recvmmsg useful standalone).
    • Enable --udp-recvmmsg by default on Linux.
    • Security hardening: port parsing, admin brute-force throttle, credential log redaction, constant-time compare, OAuth bounds checks, permission cap (#1932).
    • Add continuous latency mode to stunclient.
    • Fix test_redis_format link failure.
    • Fix configure MANPREFIX typo.
    • Fix missing sqlite3 dependendcy.
    • Fix UDP receive buffer ownership.

  • Update to version 4.12.0

    • Update khash to the latest version (#1919).
    • Update readme to match latest changes (#1920).
    • Update docs for drop-invalid-packets and response-origin-only-with-rfc5780.
    • Multiplexpeer (#1916).
    • Fix TTL/TOS type conversion (#1915).
    • turnutils_uclient: sender thread pool + UDP-GSO send batching + recv_pps reporting (#1913).
    • Fix memory leak introduced by recvmmsg path (#1912).
    • turnutils_uclient: multi-threaded listener (recv) pool.
    • examples/turnserver.conf: update description of cli option.
    • turnutils_uclient: Linux recvmmsg receive path + larger SO_RCVBUF (#1910).
    • Add UDP-GSO send path (--udp-gso) (#1907).
    • turnutils_peer: Linux fast path with drain loop, recvmmsg/sendmmsg, U… (#1908).
    • Relay recvmmsg (#1906).
    • fuzzing: use hex escapes for HTTP EOH dictionary entry.
    • Sync turnserver man page with current CLI options (#1903).
    • Remove stale --ne option from turnserver --help (#1904).
    • Restore CodeQL permissions, category, and manual build mode.

  • Update to version 4.11.0

    • Filc harness and pointer typedefs (#1896).
    • Load generator mode in turnutils_uclient (#1894).
    • Cache hot lookups in TURN data-path handlers (#1893).
    • Inline get_ioa_addr_len() in the header (#1891).
    • Trim two redundant checks from per-packet relay hot path.
    • Hoist turn_server_get_engine() out of per-packet hot path.
    • Add fuzz coverage for integrity helpers (#1888).
    • Add deterministic challenge-response builder to FuzzStun.
    • Seed address-mapping table in fuzz initializer (#1885).
    • Unblock fuzz coverage for…
Record
openSUSE-SU-2026:21184-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
coturn
Alpine:v3.23
 before 4.10.0-r0
4.10.0-r0
coturn
Alpine:v3.24
 before 4.9.0-r0
4.9.0-r0
coturn
Debian:12
 All versions, plus listed versions
4.12.0-14.14.0-14.15.0-14.18.0-14.6.1-14.6.1-2
 None known
coturn
Debian:13
 All versions, plus listed versions
4.12.0-14.14.0-14.15.0-14.18.0-14.6.1-2
 None known
coturn
Debian:14
 before 4.12.0-1, plus listed versions
4.6.1-2
4.12.0-1
coturn
Mageia:9
 before 4.6.2-1.1.mga9
4.6.2-1.1.mga9
coturn
Ubuntu:16.04:LTS
 All versions, plus listed versions
4.4.5.4-24.5.0.2-34.5.0.3-14.5.0.3-1build14.5.0.3-1ubuntu0.24.5.0.3-1ubuntu0.34.5.0.3-1ubuntu0.4
 None known
coturn
Ubuntu:18.04:LTS
 All versions, plus listed versions
4.5.0.6-1ubuntu24.5.0.7-1ubuntu14.5.0.7-1ubuntu24.5.0.7-1ubuntu2.18.04.14.5.0.7-1ubuntu2.18.04.24.5.0.7-1ubuntu2.18.04.3
 None known
coturn
Ubuntu:20.04:LTS
 All versions, plus listed versions
4.5.1.1-1.1build14.5.1.1-1.1build24.5.1.1-1.1ubuntu0.20.04.14.5.1.1-1.1ubuntu0.20.04.2
 None known
coturn
Ubuntu:22.04:LTS
 All versions, plus listed versions
4.5.2-34.5.2-3.1~ubuntu22.04.1
 None known
Show 6 moreShow less
Affected packages
PackageAffectedFixed
coturn
Ubuntu:24.04:LTS
 All versions, plus listed versions
4.6.1-1build14.6.1-1build24.6.1-1build34.6.1-1build4
 None known
coturn
Ubuntu:25.10
 All versions, plus listed versions
4.6.1-2build1
 None known
coturn
Ubuntu:26.10
 All versions, plus listed versions
4.6.1-2build24.12.0-14.14.0-14.15.0-14.18.0-1
 None known
coturn
Ubuntu:26.04:LTS
 All versions, plus listed versions
4.6.1-2build14.6.1-2build2
 None known
coturn
openSUSE:Tumbleweed
From an advisory covering 2 CVEs
 before 4.9.0-1.1
4.9.0-1.1
coturn
openSUSE:Leap 16.0
From an advisory covering 2 CVEs
 before 4.14.0-bp160.1.1
4.14.0-bp160.1.1

History

History
RecordedChangedSources
affected, facts
affected, aliases, referencesOSV
first indexedCVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-27624 is a high vulnerability (CVSS 7.2) in Coturn, published February 25, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.34%, the 28th percentile. Fixed in coturn 4.10.0-r0.

References

Show 10 moreShow less
This page doesn't list everything

Left out here: the rest of 1 source description. The JSON record has them.

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