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A critical vulnerability tracked as CVE-2026-55953 affects Erlang/OTP SSL clients using TLS 1.2 and earlier as well as DTLS, allowing an on-path attacker to bypass server authentication and intercept supposedly secure sessions. The flaw occurs because the client does not verify that the cipher suite selected by the server was actually offered in the ClientHello, enabling an attacker to force an anonymous cipher suite and complete the handshake without certificate validation or hostname checking. Once the connection is established, the attacker can read and modify traffic; TLS 1.3 is not affected because it already performs the required cipher-suite membership check.
The issue affects Erlang/OTP from OTP 17.0 up to the patched releases 27.3.4.15, 28.5.0.4, and 29.0.4, with corresponding SSL fixes in 11.2.12.11, 11.6.0.4, and 11.7.4. Erlang/OTP maintainers addressed the bug in July with code changes to ssl_handshake.erl that add a pre-TLS 1.3 client cipher-suite validation check and trigger a fatal illegal_parameter alert if the negotiated suite was not advertised by the client. The vulnerability carries a CVSS 4.0 score of 9.1 and is classified under CWE-757.
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2 events from the most recent confirmed update back to the earliest known activity.
On July 3, 2026, Erlang/OTP added a pre-TLS 1.3 client-side check to verify that the server-selected cipher suite was actually offered by the client, aborting the handshake with an illegal_parameter alert if not. The fix was committed in Erlang/OTP branches associated with releases OTP-27.3.4.15 and OTP-29.0.4.
CVE-2026-55953 was publicly documented as a critical Erlang/OTP SSL vulnerability affecting TLS 1.2 and earlier and DTLS clients, allowing an on-path attacker to force an anonymous cipher suite and bypass server authentication. The disclosure identified fixed Erlang/OTP releases 27.3.4.15, 28.5.0.4, and 29.0.4.
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Two high-severity denial-of-service vulnerabilities in Erlang/OTP's **`ssl`** application allow unauthenticated remote attackers to disrupt secure listeners before authentication completes. **`CVE-2026-55950`** affects the DTLS **`dtls_packet_demux`** component, where a time-of-check/time-of-use race condition can be triggered by rapidly sending multiple DTLS `ClientHello` messages from the same source IP address and port. Because the demultiplexing process is shared across DTLS associations on a listener, a successful crash terminates **all active DTLS sessions** on that listener rather than only the attacker's connection. A second flaw, **`CVE-2026-55952`**, affects **TLS 1.3** servers when malformed `ClientHello` pre-shared key data causes session ticket handling to crash after the software fails to validate that PSK identity and binder lists are the same length. A single crafted request can make TLS 1.3 unusable on an affected listener until the **`ssl`** application is restarted, while TLS 1.2 is not affected. Erlang/OTP maintainers released fixes in **OTP `29.0.3`**, **`28.5.0.3`**, and **`27.3.4.14`**; the DTLS issue was addressed in a GitHub commit that changed logic in **`dtls_packet_demux.erl`** to safely handle existing keys during connection state transitions.
Jul 12, 2026
Erlang/OTP users were urged to patch after multiple vulnerabilities were disclosed across the platform, including high-severity flaws that can crash BEAM nodes or exhaust resources during normal protocol handling. **CVE-2026-59251** affects `public_key` certificate path validation, where a crafted X.509 chain can trigger exponential certificate policy tree growth during a TLS handshake and consume CPU and memory until the VM fails. **CVE-2026-58227** affects the `ssl` application, where mutually cross-signed certificates can cause unbounded recursion while rebuilding incomplete TLS or DTLS peer chains, allowing an unauthenticated attacker to crash either servers or clients before authentication completes. A separate high-severity flaw, **CVE-2026-54890**, impacts the `erts` External Term Format decoder used by `binary_to_term/1`, `binary_to_term/2`, and `enif_binary_to_term()`, where an integer underflow in `BIT_BINARY_EXT` decoding can trigger near-`2^64` memory allocation and terminate the entire Erlang VM. National cyber authorities in Canada and Italy published advisories directing administrators to review Erlang security bulletins and update affected releases, while the Italian notice said the broader disclosure set includes additional Erlang/OTP issues spanning denial of service, remote code execution, authentication bypass, and security feature bypass. Fixed versions cited across the disclosures include **27.3.4.15**, **28.5.0.4**, and **29.0.4**.
Jul 29, 2026
Erlang/OTP disclosed **CVE-2025-32433** in its SSH implementation as an **unauthenticated remote code execution** vulnerability, tracked in GitHub advisory `GHSA-37cp-fgq5-7wc2`. Public descriptions characterize the issue as a **pre-authentication** flaw tied to improper handling of SSH protocol messages, including malformed `SSH_MSG_CHANNEL_REQUEST` packets, allowing attackers to execute code on exposed Erlang-based SSH servers without valid credentials. Several repositories also describe the weakness as related to missing authentication for a critical function (`CWE-306`). After disclosure, GitHub saw a rapid spread of public exploit material, including proof-of-concept code, remote shell implementations, offensive modules, lab-focused exploit scripts, and later detection tooling. Repositories from multiple authors published exploit variants in Go and other formats, along with testing tools for identifying vulnerable systems, indicating that exploitation knowledge quickly became broadly accessible to both defenders and attackers. The volume and persistence of these repositories suggest that organizations running Erlang/OTP SSH services faced elevated risk of opportunistic scanning and weaponized exploitation soon after the advisory became public.
Jul 23, 2026