Buffer Overflow in Erlang OTP SSL Application

Executive Summary

CVE-2026-55952 is a high-severity Denial-of-Service (DoS) vulnerability in the Erlang/OTP ssl application affecting TLS 1.3 servers. The vulnerability arises because the server does not validate that the Pre-Shared Key (PSK) identity list and binder list in a TLS 1.3 ClientHello message have equal lengths before processing them. When these lists are mismatched, the session ticket handler process crashes.

An unauthenticated remote attacker can exploit this by sending a single crafted ClientHello message with mismatched PSK identity and binder list lengths to a TLS 1.3 server with session tickets enabled. This causes the session ticket handler to crash, disrupting session ticket handling on that listener.

While new TLS 1.3 handshakes complete successfully, they fail when the server attempts to issue a session ticket, effectively making TLS 1.3 unusable on the affected listener until the ssl application is restarted. TLS 1.2 connections are not affected by this issue.

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Impact Analysis

This vulnerability can cause a Denial-of-Service (DoS) condition on TLS 1.3 servers using Erlang/OTP ssl with session tickets enabled. An attacker can send a single malicious ClientHello message that crashes the session ticket handler process.

As a result, while TLS 1.3 handshakes may initially succeed, the server will crash when trying to issue session tickets, rendering TLS 1.3 connections unusable on the affected listener until the ssl application or listener is restarted.

This disruption can lead to service unavailability or degraded security posture for applications relying on TLS 1.3, potentially impacting users and services dependent on secure communications.

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Detection Guidance

This vulnerability can be detected by monitoring TLS 1.3 server logs for crashes or disruptions in session ticket handling, especially after receiving ClientHello messages with malformed Pre-Shared Key (PSK) extensions where the identity list and binder list lengths do not match.

Since the issue causes the session ticket handler process to crash upon receiving a crafted ClientHello, detection can involve observing repeated TLS 1.3 handshake failures or server-side process crashes related to session ticket issuance.

There are no specific commands provided in the available resources to detect this vulnerability directly on the network or system.

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Mitigation Strategies

Immediate mitigation steps include applying the available patches that add validation checks to ensure the PSK identity list and binder list lengths match during the TLS 1.3 handshake.

If patching is not immediately possible, a workaround is to disable session tickets in the server's ssl options or restrict the server to use TLS 1.2, which is not affected by this vulnerability.

Restarting the ssl application or affected listeners after a crash can temporarily restore TLS 1.3 functionality until a patch is applied.

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Compliance Impact

The vulnerability causes a denial-of-service condition on TLS 1.3 servers by crashing the session ticket handler process when processing malformed ClientHello messages with mismatched PSK identity and binder lists.

This disruption affects the availability of TLS 1.3 connections on the affected listener until the ssl application is restarted, potentially impacting the reliability and availability of secure communications.

While the vulnerability does not directly disclose data or compromise confidentiality or integrity, the denial-of-service impact could affect compliance with standards like GDPR and HIPAA that require maintaining availability and secure communication channels.

Organizations relying on Erlang/OTP TLS 1.3 servers with session tickets enabled should consider this risk in their compliance posture and apply patches or mitigations to maintain continuous secure service availability.

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