Vulnerability · Published Oct 14, 2026 · Assigned by GitHub_M

CVE-2026-63626Mongoose: ppp_handle_ipv6cp() uses attacker-controlled length without bounds check — OOB read and heap overflow (PPP/PPPoE, MG_ENABLE_IPV6)

High 8.8

In plain English

A high-severity heap buffer overflow in mongoose from cesanta. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 15% of all known vulnerabilities). Fixed versions are available - upgrade the affected package.

Severity (CVSS 3.1)8.8High

Exploit odds (30 days)0.2%top 85.0% of all CVEs

Exploited in the wildNo reportsCISA SSVC: none

Attack toolingNoneno public tooling known

Official description

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.

Affected packages & fixed versions

Ecosystem	Package	Fixed in	Advisory
Debian:14	mongoose	7.23+ds-1	DEBIAN-CVE-2026-63626
Ubuntu:26.10	mongoose	no fix listed	UBUNTU-CVE-2026-63626

Affected products (as reported)

Vendor	Product	Versions
cesanta	mongoose	< 7.23

Weakness: CWE-122, CWE-125 · Vector: CVSS:3.1/AV:A/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

References

https://github.com/cesanta/mongoose/security/advisories/GHSA-pc66-j6r6-49x9 x_refsource_CONFIRM
https://github.com/cesanta/mongoose/commit/751f14742dea934bec08a507ab1fecc3673d4903 x_refsource_MISC
https://github.com/cesanta/mongoose/releases/tag/7.23 x_refsource_MISC