WebAssembly Micro Runtime: Missing `ref.null` heap-type validation in `load_init_expr` leaks host stack memory to the WebAssembly guest
- Exploited
- No known exploitation
- Fix
- Fixed in 2.4.5
- Who is exposed
- Not reported
Do first: Upgrade to a fixed version: 2.4.5.
- Last modified
- A 0-100 score for how much a CVE matters across the industry: exploitation, exposure, how widely the software is used, severity and whether a fix exists.What do these mean? →
- 24/100 · provisional
- Whether working attack code is public (Exploit-DB, Metasploit, Nuclei or GitHub). Public code makes attacks easier.What do these mean? →
- None on Exploit-DB, Metasploit or GitHub
Summary
WebAssembly Micro Runtime (WAMR), a lightweight standalone WebAssembly runtime, has a flaw in its default configuration (without GC enabled) where a crafted module can make the runtime copy uninitialized host stack memory into a global value readable by the guest. This can be triggered remotely, without logging in, and it discloses a small amount of host memory (four bytes for i64 or f64 globals, up to twelve bytes per v128 global).
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
Read the original description
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.
cve.now Index
- Exploitation?/40Unknown. No CISA SSVC exploitation rating yet
- Exposure17/25No login or user action needed per the CVSS vector, reachable over the network without a login · Unknown: No advisory context yet
- Reach?/20Unknown. No tracked technology or package matched
- Severity6.9/10CVSS 6.9
- No patch0/5No signal
What would change the score
- Would score about 69 if added to CISA KEV
- Would score about 64 if CISA's SSVC rates exploitation active
- Would score about 29 if advisories confirm default setups are exposed
What to do
Upgrade to a fixed version: 2.4.5.
Timeline
- CVE published
- First seen by cve.now
Affected versions
- bytecodealliance wasm-micro-runtime
fixed in 2.4.5
Evidence 4
- Advisory
- Repository
- Repository
- Repository
Corrections
None so far.
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Questions about CVE-2026-54913
Is CVE-2026-54913 being exploited?
It is not in CISA's Known Exploited Vulnerabilities catalog, and CISA's SSVC assessment does not mark exploitation as active. That does not mean it has not been attacked: vendors and researchers can report attacks before CISA lists them. No public exploit code is tracked.Source: cve.now feed data
Which versions are affected by CVE-2026-54913?
wasm-micro-runtime: before 2.4.5.Source: cve.now feed data
How do I fix CVE-2026-54913?
Upgrade to a fixed version: 2.4.5.Source: cve.now feed data