CVE-2026-27572
Wasmtime can panic when adding excessive fields to a `wasi:http/types.fields` instance
Description
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.
INFO
Published Date :
Feb. 24, 2026, 10:16 p.m.
Last Modified :
Feb. 25, 2026, 3:36 p.m.
Remotely Exploit :
Yes !
Source :
[email protected]
CVSS Scores
| Score | Version | Severity | Vector | Exploitability Score | Impact Score | Source |
|---|---|---|---|---|---|---|
| CVSS 3.1 | HIGH | [email protected] | ||||
| CVSS 4.0 | MEDIUM | [email protected] |
Solution
- Update Wasmtime to a patched version.
- Avoid adding too many fields to headers.
- Apply version 24.0.6 or later.
- Apply version 36.0.6 or later.
References to Advisories, Solutions, and Tools
Here, you will find a curated list of external links that provide in-depth
information, practical solutions, and valuable tools related to
CVE-2026-27572.
| URL | Resource |
|---|---|
| https://docs.rs/http/1.4.0/http/header/#limitations | Not Applicable |
| https://github.com/bytecodealliance/wasmtime/commit/301dc7162cca51def19131019af1187f45901c0a | Patch |
| https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.6 | Product Release Notes |
| https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.6 | Product Release Notes |
| https://github.com/bytecodealliance/wasmtime/releases/tag/v40.0.4 | Product Release Notes |
| https://github.com/bytecodealliance/wasmtime/releases/tag/v41.0.4 | Product Release Notes |
| https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-243v-98vx-264h | Third Party Advisory |
CWE - Common Weakness Enumeration
While CVE identifies
specific instances of vulnerabilities, CWE categorizes the common flaws or
weaknesses that can lead to vulnerabilities. CVE-2026-27572 is
associated with the following CWEs:
Common Attack Pattern Enumeration and Classification (CAPEC)
Common Attack Pattern Enumeration and Classification
(CAPEC)
stores attack patterns, which are descriptions of the common attributes and
approaches employed by adversaries to exploit the CVE-2026-27572
weaknesses.
We scan GitHub repositories to detect new proof-of-concept exploits. Following list is a collection of public exploits and proof-of-concepts, which have been published on GitHub (sorted by the most recently updated).
Results are limited to the first 15 repositories due to potential performance issues.
The following list is the news that have been mention
CVE-2026-27572 vulnerability anywhere in the article.
The following table lists the changes that have been made to the
CVE-2026-27572 vulnerability over time.
Vulnerability history details can be useful for understanding the evolution of a vulnerability, and for identifying the most recent changes that may impact the vulnerability's severity, exploitability, or other characteristics.
-
Initial Analysis by [email protected]
Feb. 25, 2026
Action Type Old Value New Value Added CVSS V3.1 AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Added CPE Configuration OR *cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* versions up to (excluding) 24.0.6 *cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* versions from (including) 25.0.0 up to (excluding) 36.0.6 *cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* versions from (including) 37.0.0 up to (excluding) 40.0.4 *cpe:2.3:a:bytecodealliance:wasmtime:*:*:*:*:*:rust:*:* versions from (including) 41.0.0 up to (excluding) 41.0.4 Added Reference Type GitHub, Inc.: https://docs.rs/http/1.4.0/http/header/#limitations Types: Not Applicable Added Reference Type GitHub, Inc.: https://github.com/bytecodealliance/wasmtime/commit/301dc7162cca51def19131019af1187f45901c0a Types: Patch Added Reference Type GitHub, Inc.: https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.6 Types: Product, Release Notes Added Reference Type GitHub, Inc.: https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.6 Types: Product, Release Notes Added Reference Type GitHub, Inc.: https://github.com/bytecodealliance/wasmtime/releases/tag/v40.0.4 Types: Product, Release Notes Added Reference Type GitHub, Inc.: https://github.com/bytecodealliance/wasmtime/releases/tag/v41.0.4 Types: Product, Release Notes Added Reference Type GitHub, Inc.: https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-243v-98vx-264h Types: Third Party Advisory -
New CVE Received by [email protected]
Feb. 24, 2026
Action Type Old Value New Value Added Description 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. Added CVSS V4.0 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 Added CWE CWE-770 Added Reference https://docs.rs/http/1.4.0/http/header/#limitations Added Reference https://github.com/bytecodealliance/wasmtime/commit/301dc7162cca51def19131019af1187f45901c0a Added Reference https://github.com/bytecodealliance/wasmtime/releases/tag/v24.0.6 Added Reference https://github.com/bytecodealliance/wasmtime/releases/tag/v36.0.6 Added Reference https://github.com/bytecodealliance/wasmtime/releases/tag/v40.0.4 Added Reference https://github.com/bytecodealliance/wasmtime/releases/tag/v41.0.4 Added Reference https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-243v-98vx-264h