Buffer overflow in Cesanta Mongoose
CVE-2026-63626
Mongoose is an embedded web server and network library. Prior to 7.23, ppp_handle_ipv6cp() in src/l2_ppp.c trusts the 16-bit IPv6CP len field without checking it against the received payload size. On a PPP or PPPoE link using MG_ENABLE_TCPIP and MG_ENABLE_IPV6, an unauthenticated adjacent peer can complete the required LCP exchange and send a short Configure-Request with an oversized length, causing ppp_tx_frame() to read beyond recv_queue.buf and write beyond tx.buf. The same length misuse can also expose adjacent heap bytes in a reply or hang the event loop through find_opt(). This issue is fixed in version 7.23.
Vulnerability class: Buffer Overflow
Published .
CVSS v3 metric
CVSS v3 base score 8.8 (High). Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H.
EPSS exploit prediction
No EPSS score from FIRST.org yet. New CVEs usually get one within a few days; no score means no signal yet, not low risk. How EPSS works.
Affected products
- Cesanta Mongoose — versions < 7.23
Weakness classification (CWE)
References
Frequently asked questions
- What is CVE-2026-63626?
- CVE-2026-63626 is a high-severity vulnerability in Cesanta Mongoose, classified under Heap-based Buffer Overflow. CVSS score: 8.8/10. Published 2026-10-14.
- How severe is CVE-2026-63626?
- High severity. CVSS v3 base score is 8.8 out of 10.