CVE-2026-11404
Description
A flaw was found in Mongoose. An out-of-bounds read vulnerability exists in the built-in TLS server function mg_tls_server_recv_hello(). A remote, unauthenticated attacker can exploit this by sending a specially crafted TLS ClientHello message with an oversized session ID length. This can lead to reading past the receive buffer, causing a denial of service (DoS) by crashing any HTTPS, MQTTS, or WSS service utilizing MG_TLS_BUILTIN.
Statement
An out-of-bounds read vulnerability was found in Cesanta Mongoose's built-in TLS server implementation (MG_TLS_BUILTIN). A remote, unauthenticated attacker can crash any HTTPS, MQTTS, or WSS service by sending a crafted TLS ClientHello message with an oversized session ID length. This flaw only affects deployments using Mongoose before 7.22 built-in TLS stack; services configured to use external TLS libraries (such as OpenSSL) are not vulnerable to this issue.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
An attacker could get secret values such as cryptographic keys, PII, memory addresses, or other information that could be used in additional attacks.
Confidentiality
Technical Impact: Bypass Protection Mechanism
Out-of-bounds memory could contain memory addresses or other information that can be used to bypass ASLR and other protection mechanisms in order to improve the reliability of exploiting a separate weakness for code execution.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
An attacker could cause a segmentation fault or crash by causing memory to be read outside of the bounds of the buffer. This is especially likely when the code reads a variable amount of data and assumes that a sentinel exists to stop the read operation, such as a NUL in a string.
Other
Technical Impact: Varies by Context
The read operation could produce other undefined or unexpected results.
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