CVE-2026-115391: Wasmtime 46.0.0 before 46.0.3 and 47.0.0 before 47.0.4 Unbounded Heap Allocation via WASIp3 Streams

Severity: medium (CVSS 5.8 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.2% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2026-10-22 · updated 2026-10-22
Weakness: CWE-770

Description

Wasmtime 46.0.0 before 46.0.3 and 47.0.0 before 47.0.4 contains an uncontrolled resource allocation vulnerability in its WASIp3 implementation that buffers guest-specified-length writes on the host without limit. Malicious guests can offer large buffers to WASIp3 file or HTTP write streams, causing the host to copy and buffer all bytes, bounded only by guest linear memory, exhausting host memory.

Affected products

bytecodealliance wasmtime: from 46.0.0 before 46.0.3; from 47.0.0 before 47.0.4 — fixed in 46.0.3, 47.0.4

How to fix

Upgrade to a fixed version: bytecodealliance wasmtime 46.0.3, 47.0.4. Check the vendor advisory for mitigations.

References

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