Vulnerability · Published Oct 14, 2026 · Assigned by GitHub_M
CVE-2026-73260Mongoose: Out-of-bounds Read via length-counter underflow in built-in TLS X.509 DER parser
High 7.5
In plain English
A high-severity out-of-bounds read in mongoose from cesanta. Proof-of-concept exploit code is public. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 14% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.
Official description
Mongoose is an embedded web server and network library. Prior to 7.23, the built-in TLS certificate parser selected by MG_TLS_BUILTIN fails to verify that a long-form DER element length fits within the remaining certificate buffer. In mg_der_to_tlv() and mg_der_next(), a peer-controlled length can advance the parser beyond the certificate and underflow the remaining uint32_t length, causing mg_tls_parse_cert_der() to continue walking an invalid pointer. An unauthenticated malicious TLS server, or a client presenting a certificate to a server configured for client certificates, can trigger an out-of-bounds read and denial of service during the handshake. This issue is fixed in version 7.23.
Affected packages & fixed versions
| Ecosystem | Package | Fixed in | Advisory |
|---|---|---|---|
| Debian:14 | mongoose | 7.23+ds-1 | DEBIAN-CVE-2026-73260 |
| Ubuntu:26.10 | mongoose | no fix listed | UBUNTU-CVE-2026-73260 |
Affected products (as reported)
Weakness: CWE-125 · Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
References
- https://github.com/cesanta/mongoose/security/advisories/GHSA-f6wr-mg35-p25g x_refsource_CONFIRM
- https://github.com/cesanta/mongoose/commit/a8b4ae95db3c2db85e5ad9db3fefaeebb5f7b43e x_refsource_MISC
- https://github.com/cesanta/mongoose/releases/tag/7.23 x_refsource_MISC