CVE-2026-29035
High · CVSS 8.3Published 2026-08-11
CVSS
8.3
High
EPSS
—
exploit probability
Active Exploit
No
not yet listed
What is CVE-2026-29035?
CivetWeb (commit 4a4f0c95) contains a heap and stack buffer overflow vulnerability in the read_websocket() function that allows unauthenticated remote attackers to corrupt memory by sending compressed WebSocket frames when both USE_ZLIB and MG_EXPERIMENTAL_INTERFACES are defined. Attackers can negotiate permessage-deflate during the WebSocket handshake and send a crafted frame with the RSV1 bit set, causing the server to write a 4-byte zlib sync trailer out-of-bounds past the allocated buffer, leading to heap metadata corruption, denial of service, or potential code execution.
CVSS Score Explained
CVSS 8.3 is High severity. Exploitation is likely straightforward and the impact is significant — data loss, privilege escalation, or remote code execution are common outcomes. Patch as soon as possible.
EPSS Exploitation Probability
No EPSS score yet — model needs more data on this CVE.
References & Patches
- ›https://github.com/civetweb/civetweb
- ›https://www.vulncheck.com/advisories/civetweb-heap-stack-buffer-overflow-via-websocket-permessage-deflate-decompression
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