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Fencer Vulns
high 7.5

CVE-2026-27572 json

Wasmtime can panic when adding excessive fields to a `wasi:http/types.fields` instance

published 2026-02-24 8 mo ago modified 2026-10-12 27 d ago also EUVD-2026-8569 , GHSA-243v-98vx-264h , JLSEC-2026-1353 , RUSTSEC-2026-0021

cvss
7.5
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 44%
public exploits
0
none known

Summary

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.

Patch / fix

  • crates.io wasmtime 24.0.6, 36.0.6, 40.0.4, 41.0.4
  • julia Wasmtime_jll 45.0.1+0
  • bytecodealliance wasmtime 24.0.6, 36.0.6, 40.0.4, 41.0.4
  • rust-wasmtime Debian 14 36.0.6+dfsg-1

debian advisories DEBIAN-CVE-2026-27572

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-2026-27572 updated cvss 6.3

wasmtime: Wasmtime: Denial of Service via excessive HTTP header fields

  • Red Hat Connectivity Link 1 rhcl-1/wasm-shim-rhel9
    affected: workaround, no fix available

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
8 mo ago

Exploit prediction

0.52% chance of exploitation in the next 30 days, higher than 44% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
CNA 4.0 6.9 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
CNA 4.0 6.9 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
NVD 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
OSV 3.1 7.5 CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Affected packages

ecosystem package affected fixed in
crates.io wasmtime
<24.0.6
>=25.0.0, <36.0.6
>=37.0.0, <40.0.4
>=0.0.0-0, <24.0.6
>=41.0.0, <41.0.4
24.0.6
36.0.6
40.0.4
41.0.4
julia Wasmtime_jll
<45.0.1+0
45.0.1+0

Affected products

  • bytecodealliance wasmtime

Classification

Weakness
  • CWE-770 Allocation of Resources Without Limits or Throttling

References

Sources

Fencer Vulns 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.