Heap-based Buffer Overflow Affecting cesanta/mongoose package, versions [,7.23)
Threat Intelligence
Snyk has a proof-of-concept or detailed explanation of how to exploit this vulnerability.
The probability is the direct output of the EPSS model, and conveys an overall sense of the threat of exploitation in the wild. The percentile measures the EPSS probability relative to all known EPSS scores. Note: This data is updated daily, relying on the latest available EPSS model version. Check out the EPSS documentation for more details.
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Start learning- Snyk IDSNYK-UNMANAGED-CESANTAMONGOOSE-20948701
- published15 Oct 2026
- disclosed14 Oct 2026
- creditlihnucs
Introduced: 14 Oct 2026
NewCVE-2026-63626 (opens in a new tab)How to fix?
Upgrade cesanta/mongoose to version 7.23 or higher.
Overview
cesanta/mongoose is a networking library for C/C++. It implements event-driven non-blocking APIs for TCP, UDP, HTTP, WebSocket, MQTT.
Affected versions of this package are vulnerable to Heap-based Buffer Overflow in the ppp_handle_ipv6cp function in src/l2_ppp.c, which confirms only that the frame meets the minimum header size and then passes the 16-bit len field read from it to ppp_tx_frame without comparing it against the received payload size. An attacker on the same PPP or PPPoE link can read heap memory past recv_queue.buf and have it reflected back in the IPv6CP Configure-Reject reply, and overflow the 1504-byte tx.buf by up to about 64 KB into adjacent allocations, by sending a 10-byte Configure-Request declaring len as 65535, which reaches memcpy(pay, ipv6cpp, len), while any len between 10 and 65534 instead reaches find_opt, which has no guard for p[1] == 0 and loops forever on a zero byte, hanging the event loop with no recovery short of a restart. This requires a build with MG_ENABLE_TCPIP=1 and MG_ENABLE_IPV6=1 over a PPP or PPPoE link layer, plus s_link set by a prior LCP exchange, which the attacker also drives.