An exploitable unsafe default configuration vulnerability exists in the TURN server function of coTURN prior to version 4.5.0.9. By default, the TURN server runs an unauthenticated telnet admin portal on the loopback interface. This can provide administrator access to the TURN server configuration, which can lead to additional attacks. An attacker who can get access to the telnet port can gain administrator access to the TURN server.

An exploitable SQL injection vulnerability exists in the administrator web portal function of coTURN prior to version 4.5.0.9. A login message with a specially crafted username can cause an SQL injection, resulting in authentication bypass, which could give access to the TURN server administrator web portal. An attacker can log in via the external interface of the TURN server to trigger this vulnerability.

coturn is a free open source implementation of TURN and STUN Server. Versions 4.6.2r5 through 4.7.0-r4 have a bad random number generator for nonces and port randomization after refactoring. Additionally, random numbers aren't generated with openssl's RANDbytes but libc's random() (if it's not running on Windows). When fetching about 50 sequential nonces (i.e., through sending 50 unauthenticated allocations requests) it is possible to completely reconstruct the current state of the random number generator, thereby predicting the next nonce. This allows authentication while spoofing IPs. An attacker can send authenticated messages without ever receiving the responses, including the nonce (requires knowledge of the credentials, which is e.g., often the case in IoT settings). Since the port randomization is deterministic given the pseudorandom seed, an attacker can exactly reconstruct the ports and, hence predict the randomization of the ports. If an attacker allocates a relay port, they know the current port, and they are able to predict the next relay port (at least if it is not used before). Commit 11fc465f4bba70bb0ad8aae17d6c4a63a29917d9 contains a fix.

An exploitable unsafe default configuration vulnerability exists in the TURN server functionality of coTURN prior to 4.5.0.9. By default, the TURN server allows relaying external traffic to the loopback interface of its own host. This can provide access to other private services running on that host, which can lead to further attacks. An attacker can set up a relay with a loopback address as the peer on an affected TURN server to trigger this vulnerability.

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/nsturnioaddr.c" do not check "IN6ISADDRV4MAPPED". "ioaaddrisloopback()" checks "127.x.x.x" (AFINET) and "::1" (AFINET6), but not "::ffff:127.0.0.1." "ioaaddriszero()" checks "0.0.0.0" and "::", but not "::ffff:0.0.0.0." "addrlesseq()" used by "ioaaddrinrange()" for "denied-peer-ip" matching: when the range is AFINET and the peer is AFINET6, 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.

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.