CVE-2026-90648 Memory corruption in wabt
A missing calloc check in wasm2c allows sandbox escape and arbitrary code execution on 32-bit systems or under memory pressure, affecting applications like Firefox.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Local or same network only
- Victim action needed
- Not needed
- Fix
- Available
What is CVE-2026-90648?
CVE-2026-90648 is a high-severity memory corruption vulnerability in WebAssembly wabt, published on 12 Sep 2026. It can only be exploited from the same machine or local network, with no action from the victim.
Official description
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 under memory pressure. On 64-bit Linux with default overcommit the allocation succeeds and the defect is not triggered. The wasm2c memory allocator aborts on calloc failure in the same runtime; the table allocator lacks this abort behavior. This was introduced in commit ab9e0b55 (PR #813).
Weakness: CWE-252
Which versions are affected by CVE-2026-90648?
How do I fix CVE-2026-90648?
Apply the vendor's patch.
Upgrade to the fixed version. Memory-safe languages, compiler hardening and fuzzing prevent most new cases. More about Memory corruption.
Is CVE-2026-90648 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-90648 exists.
Sources
Also known as DEBIAN-CVE-2026-90648, GHSA-7jjw-49wp-pr5h, UBUNTU-CVE-2026-90648.