CVE-2023-26489
📋 TL;DR
A memory corruption vulnerability in Wasmtime's Cranelift code generator allows WebAssembly modules to read/write memory beyond their allocated bounds. This affects x86_64 systems running vulnerable Wasmtime versions, potentially allowing malicious modules to access memory belonging to other WebAssembly instances or the host system.
💻 Affected Systems
- Wasmtime
📦 What is this software?
Cranelift Codegen by Bytecodealliance
Cranelift Codegen by Bytecodealliance
Cranelift Codegen by Bytecodealliance
Wasmtime by Bytecodealliance
Wasmtime by Bytecodealliance
Wasmtime by Bytecodealliance
⚠️ Risk & Real-World Impact
Worst Case
Complete compromise of WebAssembly sandbox isolation, allowing malicious modules to read/write memory of other instances or host processes, potentially leading to arbitrary code execution.
Likely Case
Memory corruption leading to data leakage between WebAssembly instances, application crashes, or denial of service.
If Mitigated
Minimal impact with proper guard pages or bounds checking enabled, though performance degradation may occur.
🎯 Exploit Status
Exploitation requires a malicious WebAssembly module to be loaded and executed. The vulnerability is in the runtime itself, not requiring specific module features.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: 4.0.1, 5.0.1, or 6.0.1
Vendor Advisory: https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-ff4p-7xrq-q5r8
Restart Required: Yes
Instructions:
1. Identify current Wasmtime version. 2. Update to Wasmtime 4.0.1, 5.0.1, or 6.0.1 using your package manager or from source. 3. Restart all services using Wasmtime. 4. Recompile any affected WebAssembly modules if necessary.
🔧 Temporary Workarounds
Enable explicit bounds checking
allForce all memory accesses to be explicitly bounds-checked, preventing the bug from being exploitable.
Config::static_memory_maximum_size(0)
Increase guard pages
allReserve large guard pages after linear memory to ensure out-of-bounds accesses hit unmapped memory.
Config::static_memory_guard_size(1 << 36)
🧯 If You Can't Patch
- Switch to AArch64 architecture if possible, as the bug only affects x86_64.
- Analyze existing WebAssembly modules for suspicious behavior and anomalous trap counts.
🔍 How to Verify
Check if Vulnerable:
Check Wasmtime version: if below 4.0.1, 5.0.1, or 6.0.1 and running on x86_64, the system is vulnerable.Check Version:
wasmtime --versionVerify Fix Applied:
Confirm Wasmtime version is 4.0.1, 5.0.1, or 6.0.1 or higher. Test with known malicious modules to ensure bounds are enforced.📡 Detection & Monitoring
Log Indicators:
- Anomalous number of WebAssembly traps
- Memory access violation logs
- Unexpected process crashes
Network Indicators:
- Unusual network traffic from WebAssembly runtime processes
SIEM Query:
Process execution where command_line contains 'wasmtime' AND version < '4.0.1' OR version < '5.0.1' OR version < '6.0.1'🔗 References
- https://docs.rs/wasmtime/latest/wasmtime/struct.Config.html#method.static_memory_guard_size
- https://docs.rs/wasmtime/latest/wasmtime/struct.Config.html#method.static_memory_maximum_size
- https://github.com/bytecodealliance/wasmtime/commit/63fb30e4b4415455d47b3da5a19d79c12f4f2d1f
- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-ff4p-7xrq-q5r8
- https://groups.google.com/a/bytecodealliance.org/g/sec-announce/c/Mov-ItrNJsQ
- https://docs.rs/wasmtime/latest/wasmtime/struct.Config.html#method.static_memory_guard_size
- https://docs.rs/wasmtime/latest/wasmtime/struct.Config.html#method.static_memory_maximum_size
- https://github.com/bytecodealliance/wasmtime/commit/63fb30e4b4415455d47b3da5a19d79c12f4f2d1f
- https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-ff4p-7xrq-q5r8
- https://groups.google.com/a/bytecodealliance.org/g/sec-announce/c/Mov-ItrNJsQ
