CVE-2026-27572

6.9 MEDIUM 0.5% exploit odds Fix listed Denial of service Library

What it is

Wasmtime is a runtime for WebAssembly. Prior to versions 24.0.6, 36.0.6, 4.0.04, 41.0.4, and 42.0.0, Wasmtime's implementation of the `wasi:http/types.fields` resource is susceptible to panics when too many fields are added to the set of headers. Wasmtime's implementation in the `wasmtime-wasi-http` crate is backed by a data structure which panics when it reaches excessive capacity and this condition was not handled gracefully in Wasmtime. Panicking in a WASI implementation is a Denial of Service vector for embedders and is treated as a security vulnerability in Wasmtime. Wasmtime 24.0.6, 36.0.6, 40.0.4, 41.0.4, and 42.0.0 patch this vulnerability and return a trap to the guest instead of panicking. There are no known workarounds at this time. Embedders are encouraged to update to a patched version of Wasmtime.

At a glance

Exploitability: Can be exploited over the network with a low-privilege account, but needs a user to act. High risk of service disruption.
Exploit odds: 0.5% chance of exploitation in the next 30 days (EPSS).
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2026-02-24 22:16 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-06-17 10:27 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 0.5% in the next 30 days (EPSS).
Severity: 6.9 MEDIUM (CVSS).
Fix: a patch or advisory is linked.

Details

Published: 2026-02-24 22:16 UTC
Last modified: 2026-06-17 10:27 UTC
Exploit probability: 0.5% · EPSS, next 30 days
Weakness: CWE-770 · Allocation without limits
Record status: Analyzed

Affected

Bytecodealliance Wasmtime < 24.0.6
Bytecodealliance Wasmtime < 36.0.6
Bytecodealliance Wasmtime < 40.0.4
Bytecodealliance Wasmtime < 41.0.4

Attack profile CVSS 4.0 · 6.9

Attack vector: Network
Complexity: Low
Attack requirements: Present
Privileges needed: Low
User interaction: Passive
Confidentiality: None
Integrity: None
Availability: High

Raw vector

CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:P/VC:N/VI:N/VA:H/SC:N/SI:N/SA:H/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

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2026-27572.md and follow it. Check whether this project is affected by CVE-2026-27572. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record