CVE-2026-73260 Mongoose: Out-of-bounds Read via length-counter underflow in built-in TLS X.509 DER parser
An unauthenticated attacker can cause a denial of service via out-of-bounds read in Mongoose's built-in TLS parser when enabled.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-73260?
CVE-2026-73260 is a high-severity memory corruption vulnerability in cesanta mongoose, published on 14 Oct 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.
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.
Weakness: CWE-125
Which versions are affected by CVE-2026-73260?
How do I fix CVE-2026-73260?
Upgrade to a fixed version.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-73260 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-73260 exists.
Sources
Also known as DEBIAN-CVE-2026-73260, GHSA-f6wr-mg35-p25g, UBUNTU-CVE-2026-73260.