CVE-2026-115893
Description
A flaw was found in Wasmtime. When compiling WebAssembly (Wasm) branch table instructions with an unusually large number of targets on 64-bit ARM (AArch64) systems, the Cranelift compiler backend generates an incorrect branch target. An attacker supplying a specially crafted WebAssembly module can exploit this vulnerability to redirect execution to arbitrary code offsets, allowing the module to escape the runtime sandbox and execute arbitrary code on the host system.
Statement
Red Hat rates this vulnerability as Important because an attacker executing untrusted WebAssembly bytecode can bypass runtime sandbox restrictions and achieve arbitrary code execution in the context of the host process. The risk is constrained primarily to 64-bit ARM (aarch64) environments that evaluate untrusted or maliciously crafted modules containing unusually large multi-target branch tables. Deployments on other CPU architectures or those processing only verified, internal WebAssembly payloads are not exposed to this escape vector.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base, or stability.
--- CME Mitigation Guidance (2026-11-02) ---
Disclaimer: The following mitigation solutions are provided as a courtesy, pending the application of an official patch. This content was generated utilizing AI tools in conjunction with data from https://cmetaxonomy.org. Customers are advised to independently evaluate and test these temporary mitigations within their own infrastructure.
The highest-value action is to validate and bound the maximum number of targets allowed in WebAssembly br_table instructions before Cranelift compilation: upgrade to Wasmtime 36.0.19, 48.0.7, 49.0.4 (or the fixed Tree Sitter/Rhcl 1/Wasm Shim Rhel/Virt Firmware Rs builds), which append the default target to the end of the jump table and clamp out-of-bounds indices using a conditional select instruction instead of a conditional branch, closing crafted WebAssembly module with an oversized br_table instruction. Until patched, this is only a concern on 64-bit ARM (AArch64) hosts running Wasmtime with Cranelift compiling untrusted WebAssembly modules — deployments on non-AArch64 architectures or environments executing only verified internal WebAssembly payloads are unaffected — so restrict or audit the ingestion and execution of untrusted WebAssembly modules containing oversized br_table jump tables, or limit Cranelift compilation on AArch64 systems. As a compensating measure, restrict or disable JIT compilation via Cranelift for untrusted WebAssembly modules, deploy an EDR agent to monitor for anomalous host processes, unauthorized payloads, or sandbox escape activity, and use Falco or eBPF runtime security to detect unexpected system calls and host process spawning following runtime escape. These controls limit blast radius and contain exploitation, but they do not fix the underlying branch target offset wrapping defect — apply the upstream patch to fully remediate.
Highest-impact CME: CME-1311 Input Size and Quantity Bounds Enforcement (high)
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 8.8 | N/A | 9.9 |
| Attack Vector | Local | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Changed | N/A | Changed |
| Confidentiality | High | N/A | High |
| Integrity Impact | High | N/A | High |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:H/A:H
Understanding the Weakness (CWE)
Availability
Technical Impact: DoS: Crash, Exit, or Restart; DoS: Resource Consumption (Memory); DoS: Instability
This weakness can generally lead to undefined behavior and therefore crashes. When the calculated result is used for resource allocation, this weakness can cause too many (or too few) resources to be allocated, possibly enabling crashes if the product requests more resources than can be provided. If the calculated result involves time values, then the product might crash when it encounters a time that is less than the previously-calculated time.
Integrity
Technical Impact: Modify Memory
If the value in question is important to data (as opposed to flow), simple data corruption has occurred. Also, if the overflow/wraparound results in other conditions such as buffer overflows, further memory corruption may occur.
Confidentiality,Availability,Access Control
Technical Impact: Execute Unauthorized Code or Commands; Bypass Protection Mechanism
This weakness can sometimes trigger buffer overflows, which can be used to execute arbitrary code. This is usually outside the scope of the product's implicit security policy.
Availability,Other
Technical Impact: Alter Execution Logic; DoS: Crash, Exit, or Restart; DoS: Resource Consumption (CPU)
If the overflow/wraparound occurs in a loop index variable, this could cause the loop to terminate at the wrong time - too early, too late, or not at all (i.e., infinite loops). With too many iterations, some loops could consume too many resources such as memory, file handles, etc., possibly leading to a crash or other DoS.
Access Control
Technical Impact: Bypass Protection Mechanism
If integer values are used in security-critical decisions, such as calculating quotas or allocation limits, integer overflows can be used to cause an incorrect security decision.
Access Control
Technical Impact: Bypass Protection Mechanism; DoS: Crash, Exit, or Restart
If integer values are used in time-based, security-critical decisions, such as calculating expiration times or determining whether an event occurs within a specific time or date range, to cause an incorrect security decision. The consequences could even include "self-DoS" if the overflow produces a time value that is not accounted for in protection mechanism logic [REF-1570].
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