CVE-2024-47763 [Medium] | Security Vulnerability in Wasmtime

Wasmtime is an open source runtime for WebAssembly. Wasmtime's implementation of WebAssembly tail calls combined with stack traces can result in a runtime crash in certain WebAssembly modules. The runtime crash may be undefined behavior if Wasmtime was compiled with Rust 1.80 or prior. The runtime crash is a deterministic process abort when Wasmtime is compiled with Rust 1.81 and later. WebAssembly tail calls are a proposal which relatively recently reached stage 4 in the standardization process. Wasmtime first enabled support for tail calls by default in Wasmtime 21.0.0, although that release contained a bug where it was only on-by-default for some configurations. In Wasmtime 22.0.0 tail calls were enabled by default for all configurations. The specific crash happens when an exported function in a WebAssembly module (or component) performs a `return_call` (or `return_call_indirect` or `return_call_ref`) to an imported host function which captures a stack trace (for example, the host function raises a trap). In this situation, the stack-walking code previously assumed there was always at least one WebAssembly frame on the stack but with tail calls that is no longer true. With the tail-call proposal it's possible to have an entry trampoline appear as if it directly called the exit trampoline. This situation triggers an internal assert in the stack-walking code which raises a Rust `panic!()`. When Wasmtime is compiled with Rust versions 1.80 and prior this means that an `extern "C"` function in Rust is raising a `panic!()`. This is technically undefined behavior and typically manifests as a process abort when the unwinder fails to unwind Cranelift-generated frames. When Wasmtime is compiled with Rust versions 1.81 and later this panic becomes a deterministic process abort. Overall the impact of this issue is that this is a denial-of-service vector where a malicious WebAssembly module or component can cause the host to crash. There is no other impact at this time other than availability of a service as the result of the crash is always a crash and no more. This issue was discovered by routine fuzzing performed by the Wasmtime project via Google's OSS-Fuzz infrastructure. We have no evidence that it has ever been exploited by an attacker in the wild. All versions of Wasmtime which have tail calls enabled by default have been patched: * 21.0.x - patched in 21.0.2 * 22.0.x - patched in 22.0.1 * 23.0.x - patched in 23.0.3 * 24.0.x - patched in 24.0.1 * 25.0.x - patched in 25.0.2. Wasmtime versions from 12.0.x (the first release with experimental tail call support) to 20.0.x (the last release with tail-calls off-by-default) have support for tail calls but the support is disabled by default. These versions are not affected in their default configurations, but users who explicitly enabled tail call support will need to either disable tail call support or upgrade to a patched version of Wasmtime. The main workaround for this issue is to disable tail support for tail calls in Wasmtime, for example with `Config::wasm_tail_call(false)`. Users are otherwise encouraged to upgrade to patched versions.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-06-15	0.01%	0.24%	+0.24%
2	2025-11-21	0.12%	0.01%	-0.12%
3	2025-11-18	—	0.12%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-06-15

0.01%

0.24%

+0.24%

2025-11-21

0.12%

0.01%

-0.12%

2025-11-18

—

0.12%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
5.5	3.1	MEDIUM	`CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H` Click to expand Attack vector (AV:L) They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by. Attack complexity (AC:L) Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup. Privileges required (PR:L) A normal user session is enough; they don’t have to be admin. User interaction (UI:N) Nobody has to click “OK” or open a trap file; it can work without a victim helping. Scope (S:U) Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems. Confidentiality (C:N) Doesn’t really leak secrets in a meaningful way. Integrity (I:N) Data isn’t meaningfully altered or forged. Availability (A:H) Could take the service down hard or make it unusable for people who depend on it.	1.8	3.6	[email protected]

Base score

Version

Severity

Vector

Exploitability

Impact

Score source

5.5

3.1

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:H Click to expand

Attack vector (AV:L): They already need access on the box, or another person has to do something wrong; it’s not a remote drive-by.
Attack complexity (AC:L): Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:L): A normal user session is enough; they don’t have to be admin.
User interaction (UI:N): Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U): Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N): Doesn’t really leak secrets in a meaningful way.
Integrity (I:N): Data isn’t meaningfully altered or forged.
Availability (A:H): Could take the service down hard or make it unusable for people who depend on it.

1.8

3.6

[email protected]

OS Trackers for CVE-2024-47763

vendor	priority	summary	link
`debian`	not yet assigned	CVE-2024-47763 not yet assigned priority: Debian including 1 source packages (rust-wasmtime), 3 status rows across 3 suites (forky, sid, trixie): resolved 3.	https://security-tracker.debian.org/tracker/CVE-2024-47763
`redhat`	medium	—	https://access.redhat.com/security/cve/CVE-2024-47763
`ubuntu`	medium	CVE-2024-47763 medium priority: Ubuntu including 1 source packages (rust-wasmtime), 7 status rows across 7 suites (focal, jammy, noble, oracular, plucky, questing, upstream): needs-triage 3, DNE 2, ignored 2.	https://ubuntu.com/security/CVE-2024-47763

Affected software / configurations for CVE-2024-47763

Vendor	Product	Version	Raw CPE
bytecodealliance	wasmtime	21.0.0	cpe:2.3:a:bytecodealliance:wasmtime:21.0.0:::::rust::
bytecodealliance	wasmtime	21.0.1	cpe:2.3:a:bytecodealliance:wasmtime:21.0.1:::::rust::
bytecodealliance	wasmtime	22.0.0	cpe:2.3:a:bytecodealliance:wasmtime:22.0.0:::::rust::
bytecodealliance	wasmtime	23.0.0	cpe:2.3:a:bytecodealliance:wasmtime:23.0.0:::::rust::
bytecodealliance	wasmtime	23.0.1	cpe:2.3:a:bytecodealliance:wasmtime:23.0.1:::::rust::
bytecodealliance	wasmtime	23.0.2	cpe:2.3:a:bytecodealliance:wasmtime:23.0.2:::::rust::
bytecodealliance	wasmtime	24.0.0	cpe:2.3:a:bytecodealliance:wasmtime:24.0.0:::::rust::
bytecodealliance	wasmtime	25.0.0	cpe:2.3:a:bytecodealliance:wasmtime:25.0.0:::::rust::
bytecodealliance	wasmtime	25.0.1	cpe:2.3:a:bytecodealliance:wasmtime:25.0.1:::::rust::

References for CVE-2024-47763

URL	Tags
https://docs.rs/wasmtime/latest/wasmtime/struct.Config.html#method.wasm_tail_call	Product
https://github.com/WebAssembly/proposals	Product
https://github.com/bytecodealliance/wasmtime/pull/8540	Product
https://github.com/bytecodealliance/wasmtime/pull/8682	Product
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-q8hx-mm92-4wvg	Mitigation Patch Third Party Advisory
https://github.com/webassembly/tail-call	Product

URL

CVE-2024-47763 | Wasmtime runtime crash when combining tail calls with trapping imports

Exploit prediction scoring system (EPSS) score for CVE-2024-47763

Common vulnerability scoring system (CVSS) metrics for CVE-2024-47763

Weakness enumeration for CVE-2024-47763

GitHub Security Advisory for CVE-2024-47763

OS Trackers for CVE-2024-47763

Affected software / configurations for CVE-2024-47763

References for CVE-2024-47763