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Fencer Intel
medium 6.9

CVE-2026-54913 json

WebAssembly Micro Runtime: Missing `ref.null` heap-type validation in `load_init_expr` leaks host stack memory to the WebAssembly guest

published 3mo ago modified 2d ago also EUVD-2026-117616 , GHSA-frwm-5hpr-2hq2

Unreviewed: the maintainers' own advisory

Published by the maintainers on their GitHub repository wasm-micro-runtime/wasm-micro-runtime. GitHub has not reviewed it into the GitHub Advisory Database, so the affected packages and versions are the maintainers' word. Read the full advisory on GitHub.

cvss
6.9
version 4.0, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 23%
public exploits
0
none known

Summary

WebAssembly Micro Runtime (WAMR) is a lightweight standalone WebAssembly (Wasm) runtime. Prior to 2.4.5, load_init_expr in core/iwasm/interpreter/wasm_loader.c accepts a non-reference heap-type byte for ref.null when WASM_ENABLE_GC=0, while the local WASMValue cur_value union is not zero-initialized and setting ref_index writes only part of it. A crafted module can declare an i64, f64, or v128 global initialized through the invalid ref.null form, causing push_const_expr_stack and the later global initialization path to copy uninitialized host-stack bytes into a value readable by the guest. The classic and fast interpreters are affected in the default no-GC configuration; the GC-enabled path validates heap types. The disclosure is four bytes for i64 or f64 globals and up to twelve bytes for each v128 global. This issue is fixed in version 2.4.5.

Patch / fix

  • bytecodealliance webassembly_micro_runtime 2.4.5

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
2d ago

Exploit prediction

0.30% chance of exploitation in the next 30 days, higher than 23% of all scored CVEs (FIRST EPSS, 2026-11-11).

Exploits and checks

  • github.com https://github.com/wasm-micro-runtime/wasm-micro-runtime/security/advisories/GHSA-frwm-5hpr-2hq2 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N
CNA 4.0 6.9 CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:N/VA:N/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

Affected products

  • bytecodealliance wasm-micro-runtime

Classification

Weakness
  • CWE-457 Use of Uninitialized Variable

References

Sources

Fencer Intel keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

The maintainers of wasm-micro-runtime/wasm-micro-runtime published their own advisory on GitHub. Reviewed sources take precedence over it.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.