WAMR fast interpreter loader heap buffer overflow via constant deduplication mismatch
Affects WAMR 2.4.4 and earlier builds with the fast interpreter enabled (WAMR_BUILD_FAST_INTERP=1, the default mode). Fixed in 2.4.5.
Written by anthropic/claude-haiku-5.5 from the sources below. Verify against them.
- Exploited
- Proof of concept public, per CISA
- Fix
- Fixed in 2.4.5
- Who is exposed
- Default setups
Do first: Check every install: default setups are affected.
- 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? →
- 47/100 · provisional
- How many real-world setups can hit the bug, from the vendor's advisory and CISA data. It does not know your setup.What do these mean? →
- Default setups
- 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
- Exploitation: poc
- Automatable: no
- Technical impact: total
Summary
WAMR (WebAssembly Micro Runtime), a lightweight WebAssembly runtime, is affected by a heap buffer overflow in its fast interpreter loader, which only occurs in builds with the fast interpreter enabled. A remote attacker without logging in can supply a crafted WebAssembly module that writes data past a heap buffer during loading, which can corrupt heap metadata and crash the process, causing denial of service.
Read the original description
WebAssembly Micro Runtime (WAMR) is a lightweight standalone WebAssembly (Wasm) runtime. Prior to 2.4.5, the two-pass fast interpreter loader in core/iwasm/interpreter/wasm_loader.c can make inconsistent constant-table decisions between the sizing pass and the emitting pass. After duplicate constants inflate the first pass beyond the constant-slot limit, wasm_loader_get_const_offset emits later constants inline, but the between-pass sort and deduplication reduces the table so the second pass can choose table references and cause reserve_block_ret to emit additional copy operands that were not included in code_compiled_peak_size. A crafted module can therefore make the second pass write partially attacker-controlled compiled-code data beyond the heap buffer allocated from the first pass's size calculation during wasm_runtime_load, before guest code executes. This can corrupt host heap metadata and deterministically crash the process, causing denial of service; further consequences depend on the host application's heap layout. Builds using WAMR_BUILD_FAST_INTERP=1 are affected; disabling the fast interpreter avoids the vulnerable loader. This issue is fixed in version 2.4.5.
cve.now Index
- Exploitation15/40CISA rates a proof of concept as public
- Exposure22/25Default setups, reachable over the network without a login
- Reach?/20Unknown. No tracked technology or package matched
- Severity9.8/10CVSS 8.8, total technical impact per CISA
- No patch0/5No signal
What would change the score
- Would score about 72 if added to CISA KEV
- Would score about 67 if CISA's SSVC rates exploitation active
What to do
Check every install: default setups are affected.
Upgrade to a fixed version: 2.4.5.
Workaround: Disable the fast interpreter at build time (-DWAMR_BUILD_FAST_INTERP=0).
Timeline
- CVE published
- First seen by cve.now
- CISA SSVC assessment
Exploitation: poc · Automatable: no · Technical impact: total
- Record last updated
Affected versions
- bytecodealliance wasm-micro-runtime
fixed in 2.4.5
Evidence 4
- Advisory
- Repository
- Repository
- Link
Corrections
None so far.
Something wrong on this page? Report an error. Every fix is listed here.
Questions about CVE-2026-54912
Is CVE-2026-54912 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. CISA's SSVC assessment notes a proof of concept exists. No public exploit code is tracked.Source: cve.now feed data
What does this mean?
When WAMR loads a WebAssembly module, the fast interpreter's loader can write past the end of a heap buffer while deduplicating constants. This can corrupt heap metadata and crash the host process, causing denial of service. Further consequences depend on the host's heap layout.Source: github.com
Which versions are affected by CVE-2026-54912?
wasm-micro-runtime: before 2.4.5.Source: cve.now feed data
Am I affected, and how do I check?
Builds with WAMR_BUILD_FAST_INTERP=1, the default interpreter mode, on version 2.4.4 and earlier, including the main branch at commit dd0fee27. Prior versions with the two-pass fast interpreter loader are likely affected too. To check a build, look at its WAMR_BUILD_FAST_INTERP setting and its version.Source: github.com
How do I fix CVE-2026-54912?
Upgrade to WAMR 2.4.5, which contains the fix. If the upgrade is not possible, rebuild with the fast interpreter disabled using -DWAMR_BUILD_FAST_INTERP=0.Source: github.com