Unauthenticated memory corruption via WebSocket trailer overflow
Published Aug 11, 2026 · Updated Aug 11, 2026
Buffer overflow in CivetWeb through commit 4a4f0c95 allows unauthenticated remote attackers to corrupt memory with compressed WebSocket frames. The read_websocket() function allocates only data_len bytes before appending a four-byte zlib sync trailer, so the write overruns stack or heap storage. The path requires both USE_ZLIB and MG_EXPERIMENTAL_INTERFACES; exploitation can crash the server or execute code.
Summary
What happened
Buffer overflow in CivetWeb through commit 4a4f0c95 allows unauthenticated remote attackers to corrupt memory with compressed WebSocket frames. The read_websocket() function allocates only data_len bytes before appending a four-byte zlib sync trailer, so the write overruns stack or heap storage. The path requires both USE_ZLIB and MG_EXPERIMENTAL_INTERFACES; exploitation can crash the server or execute code.
The record
- CVE
- CVE-2026-29035
- Published
- Aug 11, 2026
- Updated
- Aug 11, 2026
- Vendor
- CivetWeb
- Product
- CivetWeb
- Classifications
- CWE-787, T1190
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 11, 2026CVE publishedPublication date reported by the CVE source.
- Aug 11, 2026Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
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- Affected versionversion=0 <=4a4f0c95
What conditions does exploitation require?
What is affected?
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Public exploit references
No public exploit references are available in this record.
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Technologies
Your stack
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Your stack
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