Severity by source
Network-reachable pre-auth TLS parsing; OOB read enables crash (A:H) and potential memory leak (C:L); no integrity impact.
Lifecycle Timeline
1DescriptionCVE.org
[mg_tls_client_recv_hello key_share extension OOB read]
AnalysisAI
Out-of-bounds read in Mongoose's TLS stack during Client Hello parsing exposes services built on this embedded networking library to remote memory disclosure or crash. The vulnerable function mg_tls_client_recv_hello fails to properly validate the bounds of the key_share extension - a TLS 1.3 construct - when processing incoming handshake messages, allowing a remote attacker to trigger the flaw without authentication before any TLS session is established. No public exploit has been identified at time of analysis, and CISA KEV listing is absent, but the pre-authentication network exposure and trivial triggering conditions make this a meaningful risk for any Mongoose-based service with TLS enabled.
Technical ContextAI
Mongoose (commonly identified by the mg_ function namespace) is an embedded C networking library by Cesanta, widely used in IoT firmware, security appliances, and lightweight server applications. The affected function mg_tls_client_recv_hello handles the TLS 1.3 ClientHello message on the server side. The key_share extension, defined in RFC 8446 Section 4.2.8, carries Diffie-Hellman or ECDH key material offered by the client during the handshake. An out-of-bounds read (consistent with CWE-125) in this parsing path occurs when the library reads beyond the allocated buffer while iterating over or extracting key_share data, likely due to missing or insufficient length validation of the extension or its sub-fields. No CPE string or CWE identifier was supplied in the source intelligence; the library association is inferred from the mg_ function prefix, which is consistent with Mongoose's documented API naming convention.
Affected ProductsAI
The affected product is the Mongoose embedded networking library, specifically its TLS client-hello parsing code in the mg_tls_client_recv_hello function. The vulnerability was reported by Ubuntu, suggesting affected versions are those packaged in Ubuntu's repositories. Exact affected version ranges have not been confirmed in the available intelligence data; affected versions should be determined by consulting the upstream Mongoose GitHub repository and Ubuntu's security tracker. No CPE string was provided in the source data.
RemediationAI
Upgrade to the patched version of Mongoose once released by Cesanta upstream. Upstream fix availability should be monitored at the Mongoose GitHub repository. Ubuntu users should apply the distribution security update for the mongoose package once published via Ubuntu Security Notices (USN). If an immediate patch is unavailable, a targeted workaround is to disable TLS 1.3 support in the Mongoose configuration if the application supports TLS 1.2 only - this prevents key_share extension processing entirely, though it reduces protocol security posture and may break clients that require TLS 1.3. Alternatively, placing a TLS-terminating proxy (such as nginx or HAProxy) in front of the Mongoose service shifts the key_share parsing to the proxy and removes the vulnerable code from the attack path. No patch version has been independently confirmed from the available data.
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External POC / Exploit Code
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