CVE-2026-55950
MediumCVSS 5.9Exploitation Probability (EPSS)
Low risk30th percentile - higher than 30% of all known CVEs
Summary
TOCTOU race condition in the ssl module (dtls_packet_demux) in Erlang/OTP. An unauthenticated remote attacker can send multiple ClientHello messages from the same source, causing a race and crash of the demux process, terminating all active DTLS sessions on that listener. The attack is repeatable and requires no authentication.
Risk Assessment
Risk of persistent denial of service (DoS) for all DTLS clients, potentially disrupting communication and service availability.
Recommendation
Update Erlang/OTP to version 29.0.3, 28.5.0.3, or 27.3.4.14 (ssl to 11.7.3, 11.6.0.3, or 11.2.12.10). Consider rate-limiting DTLS connections.
Other vulnerabilities in Erlang/OTP
See all- CVE-2026-28808Critical
In Erlang OTP (inets module), an incorrect authorization vulnerability exists. When script_alias maps a URL prefix to a directory outside DocumentRoot, mod_auth evaluates directory access controls against the DocumentRoot path while mod_cgi executes the script at the ScriptAlias path. This mismatch allows unauthenticated access to CGI scripts protected by directory rules.
- CVE-2026-23941Critical
In Erlang OTP (inets httpd module), an HTTP Request Smuggling vulnerability exists. The server does not reject or normalize duplicate Content-Length headers. The first value is used, while common proxies use the last, enabling front-end/back-end desynchronization and injection of attacker-controlled bytes as the start of the next request.
- CVE-2016-10253Critical
An issue was discovered in Erlang/OTP 18.x related to the generation of compiled regular expressions, which is vulnerable to a heap overflow. Regular expressions using a malformed extpattern can indirectly specify an offset used as an array index.
- CVE-2026-58227High
A vulnerability in the Erlang/OTP SSL application allows memory exhaustion by sending a crafted certificate chain during TLS/DTLS handshake. Lack of cycle detection in the certificate chain building function causes unbounded recursion, leading to BEAM node crash.
- CVE-2026-55953High
The TLS 1.2 (and earlier) and DTLS client in Erlang/OTP does not verify that the cipher suite selected by the server in ServerHello was among the suites offered by the client. An on-path attacker can select an anonymous cipher suite, bypassing certificate and hostname verification, allowing interception and modification of traffic.
- CVE-2026-55737High
In Erlang OTP, a signed to unsigned conversion error and out-of-bounds heap write vulnerability exists when decoding a crafted ETF binary via binary_to_term/1. This can corrupt the BEAM heap pointer and crash the virtual machine.
- CVE-2026-54890High
A vulnerability in the External Term Format (ETF) decoder in ERTS causes an integer underflow when processing crafted binary data. This leads to allocating huge memory and crashing the entire Erlang/VM node.
- CVE-2026-47078Medium
In the zip module of Erlang OTP stdlib, a relative path traversal vulnerability allows writing files outside the intended extraction directory via a crafted zip archive. The zip:check_dir_level/2 function improperly validates paths containing ../ sequences.
- CVE-2026-42792High
In Erlang OTP (epmd), a connection slot exhaustion vulnerability allows an unauthenticated remote attacker to permanently terminate the epmd daemon. The do_accept function incorrectly treats EMFILE/ENFILE errors as fatal instead of recoverable.
- CVE-2026-55952High
Vulnerability in the Erlang/OTP ssl application. An unauthenticated attacker can send a crafted TLS 1.3 ClientHello, crashing the session ticket handler and making TLS 1.3 unusable until the ssl application is restarted.
Original NVD description (English source)
Time-of-check Time-of-use (TOCTOU) race condition vulnerability in Erlang/OTP ssl (dtls_packet_demux module) allows an unauthenticated remote attacker to crash all active DTLS sessions on a listener. A DTLS server listener uses a single shared dtls_packet_demux gen_server process to route incoming UDP datagrams to the correct connection handler. When a DTLS client reconnects rapidly from the same source address and port (sending multiple ClientHello messages in quick succession), a race condition in the demux's internal gb_trees key-value store causes a {key_exists, {old, Client}} crash, terminating the demux process. Because the demux is shared across all DTLS associations on that listener, its crash immediately kills every active DTLS session, not just the attacker's. The attack is pre-authentication: the attacker only needs to send UDP datagrams containing valid ClientHello messages from the same source IP and port before the intermediate DOWN monitor message is processed by the gen_server. No credentials, no completed handshake, and no special configuration are required, and the crash can be repeated indefinitely to create a persistent denial of service for all clients of that listener. This vulnerability is associated with program file lib/ssl/src/dtls_packet_demux.erl. This issue affects OTP from OTP 25.3 before OTP 29.0.3, OTP 28.5.0.3 and OTP 27.3.4.14, corresponding to ssl from 10.9 before 11.7.3, 11.6.0.3 and 11.2.12.10.