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CVE

CVE-2026-27572

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

CVE-2026-27572

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

Impact

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.

Patches

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.

Workarounds

There are no known workarounds at this time, embedders are encouraged to update to a patched version of Wasmtime.

Resources

Package Versions Affected

Package Version
patch Availability
No items found.

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CVSS Version

Severity
Base Score
CVSS Version
Score Vector
C
H
U
6.9
-
4.0
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
C
H
U
0
-
C
H
U
-

Related Resources

No items found.

References

https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-243v-98vx-264h, https://nvd.nist.gov/vuln/detail/CVE-2026-27572, https://github.com/bytecodealliance/wasmtime/commit/301dc7162cca51def19131019af1187f45901c0a, https://docs.rs/http/1.4.0/http/header/#limitations, https://github.com/bytecodealliance/wasmtime, https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.6, https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.6, https://github.com/bytecodealliance/wasmtime/releases/tag/v40.0.4, https://github.com/bytecodealliance/wasmtime/releases/tag/v41.0.4, https://rustsec.org/advisories/RUSTSEC-2026-0021.html

Severity

7.5

CVSS Score
0
10

Basic Information

Ecosystem
Base CVSS
7.5
EPSS Probability
0.00032%
EPSS Percentile
0.09672%
Introduced Version
0,25.0.0,37.0.0
Fix Available
24.0.6,36.0.6,40.0.4,2.0.1-r0,10.0.0-r7,1.13.0-r2,0.228.0-r3,0.44.0-r0

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