CVE-2026-90648: wasm2c in WebAssembly wabt through 1.0.41 allows sandbox escape in some situations that primarily involve 32-bit platforms, aka a "table flip" attack.

wasm2c in WebAssembly wabt through 1.0.41 allows sandbox escape in some situations that primarily involve 32-bit platforms, aka a "table flip" attack.

wasm2c in WebAssembly wabt through 1.0.41 allows sandbox escape in some situations that primarily involve 32-bit platforms, aka a "table flip" attack. It does not check the return value of calloc() in wasm_rt_allocate_funcref_table() (wasm2c/wasm-rt-impl-tableops.inc). When the funcref table allocation fails, table->data is left NULL while table->size keeps the guest-declared element count; thus, bounds checks still pass and table element accesses resolve to absolute memory addresses (i * sizeof(wasm_rt_funcref_t)). This gives arbitrary read and write of host process memory and - via table.get, table.set, and call_indirect - arbitrary code execution, defeating the isolation that wasm2c exists to provide (a full sandbox escape). wasm2c is used as an in-process sandboxing boundary by RLBox and WasmBoxC, including in Firefox, which compiles the Graphite, Hunspell, Ogg, Expat, and Woff2 libraries via wasm2c to contain untrusted font, media, and XML input. Therefore, sandboxing in these applications is potentially affected. Exploitation requires the funcref table allocation to fail, for example under an address-space limit (RLIMIT_AS), on 32-bit hosts, with vm.overcommit_memory=2, or un

Description from the National Vulnerability Database, published by MITRE

What it means for a small business

If your business uses wabt, install the vendor's update. If you're not sure whether you use it, ask whoever manages your computers.

How likely is an attack? The Exploit Prediction Scoring System, run by FIRST (the global association of security response teams), puts the odds of this one being exploited in the next 30 days at 0.19%, higher than 8% of CVEs. That’s low, but low isn’t zero, and the odds jump the day someone publishes an exploit. Scored October 28, 2026, updated daily.

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Sources

Part of the Huttenlocher Technologies vulnerability database, refreshed twice a day from CISA and the NVD. The title, category and plain-language guidance are ours; check the linked record before acting on a detail. This is general guidance, not a review of your systems.

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