CVE-2026-90648

Published Sep 12, 2026 CVSS 4.0 · 7.1 High EPSS < 1% KEV · Not listed
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).

Remediation

No solution or workaround provided in the CVE record

Tracking

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Advisories

No advisories available
History
Type Values Removed Values Added
Title wasm2c Funcref Table Allocation Failure Enables Code Execution
Type Values Removed Values Added
Title wasm2c Funcref Table Allocation Failure Enables Code Execution
Type Values Removed Values Added
Title Wasm2c Sandbox Escape via Table Allocation Failure on 32‑bit Platforms
Metrics ssvc

{'options': {'Automatable': 'no', 'Exploitation': 'poc', 'Technical Impact': 'partial'}, 'version': '2.0.3'}

Type Values Removed Values Added
Title Wasm2c Sandbox Escape via Table Allocation Failure on 32‑bit Platforms
Type Values Removed Values Added
Title wasm2c Funcref Table Allocation Failure Enabling Sandbox Escape
Type Values Removed Values Added
Title wasm2c Funcref Table Allocation Failure Enabling Sandbox Escape
Type Values Removed Values Added
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).
First Time appeared Webassembly
Webassembly wabt
Weaknesses CWE-252
CPEs cpe:2.3:a:webassembly:wabt:*:*:*:*:*:*:*:*
Vendors & Products Webassembly
Webassembly wabt
References
Metrics cvssV4_0

{'score': 7.1, 'vector': 'CVSS:4.0/AV:L/AC:L/AT:P/PR:N/UI:N/VC:N/VI:H/VA:H/SC:N/SI:H/SA:H'}

Weaknesses

Sources

Status
PUBLISHED
Assigner
mitre
Published
Updated
Oct 23, 2026, 7:16 PM
Reserved
Sep 12, 2026, 11:16 PM
Status
Deferred
Published
Sep 13, 2026, 12:17 AM
Modified
Oct 23, 2026, 8:17 PM