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Fencer Intel
low 2.0

CVE-2026-104855 json

Wasmtime: Preemption and traps during bulk operations enable breaking internal VM state

published 3mo ago modified 28d ago also EUVD-2026-91765 , GHSA-2hw9-mc66-jc2q , RUSTSEC-2026-0223

cvss
2.0
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 20%
public exploits
0
none known

Summary

Wasmtime is a runtime for WebAssembly. From 46.0.0 until 46.0.2 and 47.0.3, fuel and epoch preemption checks inside bulk operations including memory.copy, table.grow, and array.copy can expose invalid intermediate state when an embedder mutates a Store in Store::epoch_deadline_callback or continues using a Store after cancellation or a trap. A cancelled non-nullable table growth can leave null elements, linear-memory growth during memory.copy can invalidate retained raw pointers, and callback-triggered garbage collection during array.copy can invalidate GC pointers, resulting in a crash, invalid memory access, or GC heap corruption. Embeddings whose callbacks only access the host data in Store<T>, and embeddings that discard a Store after timeout or epoch deadline, are not affected. This issue is fixed in versions 46.0.2 and 47.0.3.

Patch / fix

  • crates.io wasmtime 46.0.2, 47.0.3
  • bytecodealliance wasmtime 46.0.2, 47.0.3

Is CVE-2026-104855 in your dependencies? Fencer shows which of your repositories are affected as soon as an advisory lands, and opens the fix as a pull request.

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Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-104855 updated cvss 4.7

wasmtime: wasmtime: Memory corruption via preemption checks during bulk operations

  • Red Hat Connectivity Link 1 rhcl-1/wasm-shim-rhel9 Red Hat Enterprise Linux 10 tree-sitter 0.23.0-3.el10, virt-firmware-rs 26.4-1.el10
    affected: workaround, no fix available “Fix deferred”
  • Red Hat Hardened Images rust 1.98.1-1.hum1, openshell 0.1.2-0.2.hum1
    not affected: component not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
none
Automatable
no
Technical impact
partial
Assessed
last mo.

Exploit prediction

0.28% chance of exploitation in the next 30 days, higher than 20% of all scored CVEs (FIRST EPSS, 2026-11-09).

CVSS scores

assigned by version score vector
CNA 4.0 2.0 CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:P/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N
CNA 4.0 2.0 CVSS:4.0/AV:N/AC:H/AT:P/PR:H/UI:P/VC:N/VI:L/VA:L/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 packages

ecosystem package affected fixed in
crates.io wasmtime
>=46.0.0, <46.0.2
>=47.0.0, <47.0.3
46.0.2
47.0.3

Affected products

  • bytecodealliance wasmtime

Classification

Weakness
  • CWE-362 Concurrent Execution using Shared Resource with Improper Synchronization

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.

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