Severity by source
Network-reachable via TLS handshake (AV:N), but OOB read on crafted ECDSA integers requires specific certificate construction (AC:H); no authentication needed pre-handshake (PR:N); crash or partial memory leak, no integrity impact.
Estimated by vuln.today — no official severity rating has been published for this CVE yet.
Lifecycle Timeline
1DescriptionCVE.org
[mg_tls_verify_cert_signature OOB read for short ECDSA integers]
AnalysisAI
Out-of-bounds read in Mongoose's TLS certificate signature verification function mg_tls_verify_cert_signature when processing ECDSA signatures containing short integer components (r or s values). Network-connected applications embedding the Mongoose C networking library are exposed when acting as a TLS client or server that verifies peer certificates containing malformed, truncated ECDSA integer fields. An unauthenticated remote attacker can supply a crafted certificate to trigger the OOB read, potentially leaking process memory or causing a crash. No public exploit code has been identified at time of analysis and no KEV listing is present.
Technical ContextAI
Mongoose (formerly Cesanta Mongoose) is a widely embedded C networking library providing HTTP, MQTT, and TLS functionality for IoT and embedded-systems firmware. Its internal TLS stack implements ECDSA certificate verification via mg_tls_verify_cert_signature. ECDSA signatures are DER-encoded ASN.1 SEQUENCE structures containing two INTEGERs (r and s). When a signer produces a value with leading zero bytes, the DER encoding is shorter than the field size - a legitimate scenario the verifier must handle. The OOB read indicates the function fails to validate the actual byte length of these integer fields before accessing memory, reading past the allocated buffer. This is a classic CWE-125 (Out-of-Bounds Read) pattern in hand-rolled ASN.1/DER parsers in C. No CPE strings or CWE identifiers were supplied in the source intelligence; this attribution is inferred from the function name and Mongoose API conventions.
Affected ProductsAI
The affected product is the Mongoose embedded networking library (Cesanta), specifically the mg_tls subsystem responsible for TLS certificate signature verification. The exact affected version range is not confirmed in the available intelligence - the only source is a Ubuntu vendor report, which suggests Ubuntu packages that bundle Mongoose may be affected. No CPE strings or advisory links were supplied. Consumers of Mongoose in firmware, IoT devices, or server applications that verify peer TLS certificates with ECDSA signatures should consult the upstream Cesanta Mongoose GitHub repository and any applicable Ubuntu security advisories for patched package versions.
RemediationAI
No exact patch version is confirmed from the available data - patch status is unverified pending a vendor advisory. Upgrade to the latest Mongoose release from the upstream Cesanta repository as soon as a fix is published. Ubuntu users should monitor Ubuntu Security Notices (USN) for a patched package update and apply it via standard apt tooling. As a compensating control, restrict which certificate authorities are trusted in the Mongoose TLS configuration to reduce the attack surface from untrusted peers presenting malformed certificates. If Mongoose is deployed in a client context, pin expected server certificates to prevent a malicious server from supplying a crafted certificate. If mutual TLS (mTLS) is enabled, temporarily restricting client-certificate verification removes the inbound attack vector but eliminates client authentication - weigh this trade-off against exposure. No patch version has been independently confirmed from the available data.
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External POC / Exploit Code
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