CVE-2026-24116 [Medium] | Out-of-bounds Read in Wasmtime

Wasmtime is a runtime for WebAssembly. Starting in version 29.0.0 and prior to version 36.0.5, 40.0.3, and 41.0.1, on x86-64 platforms with AVX, Wasmtime's compilation of the `f64.copysign` WebAssembly instruction with Cranelift may load 8 more bytes than is necessary. When signals-based-traps are disabled this can result in a uncaught segfault due to loading from unmapped guard pages. With guard pages disabled it's possible for out-of-sandbox data to be loaded, but unless there is another bug in Cranelift this data is not visible to WebAssembly guests. Wasmtime 36.0.5, 40.0.3, and 41.0.1 have been released to fix this issue. Users are recommended to upgrade to the patched versions of Wasmtime. Other affected versions are not patched and users should updated to supported major version instead. This bug can be worked around by enabling signals-based-traps. While disabling guard pages can be a quick fix in some situations, it's not recommended to disabled guard pages as it is a key defense-in-depth measure of Wasmtime.

#	Date	Old EPSS score	New EPSS score	Delta (New - Old)
1	2026-01-28	—	0.01%	—

Date

Old EPSS score

New EPSS score

Delta (New - Old)

2026-01-28

—

0.01%

—

Base score	Version	Severity	Vector	Exploitability	Impact	Score source
4.1	4.0	MEDIUM	`CVSS:4.0/AV:L/AC:L/AT:P/PR:L/UI:A/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/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` Click to expand Attack vector (AV:L) Attacker needs local access on the target system. Attack complexity (AC:L) Exploitation conditions are straightforward and stable. Attack requirements (AT:P) Additional preconditions must be present for exploitation. Privileges required (PR:L) Low privileges are required. User interaction (UI:A) User interaction is required in an active way. Vulnerable system confidentiality impact (VC:N) No confidentiality impact on the vulnerable system. Vulnerable system integrity impact (VI:N) No integrity impact on the vulnerable system. Vulnerable system availability impact (VA:H) High availability impact on the vulnerable system. Subsequent system confidentiality impact (SC:N) No confidentiality impact on subsequent systems. Subsequent system integrity impact (SI:N) No integrity impact on subsequent systems. Subsequent system availability impact (SA:N) No availability impact on subsequent systems. Exploit maturity (threat) (E:X) Not defined: no reliable threat intelligence; scoring assumes the worst case (equivalent to Attacked). Confidentiality requirement (CR:X) Not defined: insufficient information; scoring treats this like High (worst case). Integrity requirement (IR:X) Not defined: insufficient information; scoring treats this like High (worst case). Availability requirement (AR:X) Not defined: insufficient information; scoring treats this like High (worst case). Modified attack vector (MAV:X) Not defined: scoring uses the Base Attack Vector (AV). Modified attack complexity (MAC:X) Not defined: scoring uses the Base Attack Complexity (AC). Modified attack requirements (MAT:X) Not defined: scoring uses the Base Attack Requirements (AT). Modified privileges required (MPR:X) Not defined: scoring uses the Base Privileges Required (PR). Modified user interaction (MUI:X) Not defined: scoring uses the Base User Interaction (UI). Modified vulnerable system confidentiality impact (MVC:X) Not defined: scoring uses the Base VC metric. Modified vulnerable system integrity impact (MVI:X) Not defined: scoring uses the Base VI metric. Modified vulnerable system availability impact (MVA:X) Not defined: scoring uses the Base VA metric. Modified subsequent system confidentiality impact (MSC:X) Not defined: scoring uses the Base SC metric. Modified subsequent system integrity impact (MSI:X) Not defined: scoring uses the Base SI metric. Modified subsequent system availability impact (MSA:X) Not defined: scoring uses the Base SA metric. Safety (supplemental) (S:X) Not evaluated. Automatable (supplemental) (AU:X) Not evaluated. Recovery (supplemental) (R:X) Not evaluated. Value density (supplemental) (V:X) Not evaluated. Vulnerability response effort (supplemental) (RE:X) Not evaluated. Provider urgency (supplemental) (U:X) Not evaluated.	—	—	[email protected]
5.5	3.1	MEDIUM	`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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:N) No account or special rights needed—anonymous or random user is enough. User interaction (UI:R) A real person has to do something—click, install, enable—otherwise it doesn’t land. 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

4.1

4.0

MEDIUM

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

Click to expand

Attack vector (AV:L): Attacker needs local access on the target system.
Attack complexity (AC:L): Exploitation conditions are straightforward and stable.
Attack requirements (AT:P): Additional preconditions must be present for exploitation.
Privileges required (PR:L): Low privileges are required.
User interaction (UI:A): User interaction is required in an active way.
Vulnerable system confidentiality impact (VC:N): No confidentiality impact on the vulnerable system.
Vulnerable system integrity impact (VI:N): No integrity impact on the vulnerable system.
Vulnerable system availability impact (VA:H): High availability impact on the vulnerable system.
Subsequent system confidentiality impact (SC:N): No confidentiality impact on subsequent systems.
Subsequent system integrity impact (SI:N): No integrity impact on subsequent systems.
Subsequent system availability impact (SA:N): No availability impact on subsequent systems.
Exploit maturity (threat) (E:X): Not defined: no reliable threat intelligence; scoring assumes the worst case (equivalent to Attacked).
Confidentiality requirement (CR:X): Not defined: insufficient information; scoring treats this like High (worst case).
Integrity requirement (IR:X): Not defined: insufficient information; scoring treats this like High (worst case).
Availability requirement (AR:X): Not defined: insufficient information; scoring treats this like High (worst case).
Modified attack vector (MAV:X): Not defined: scoring uses the Base Attack Vector (AV).
Modified attack complexity (MAC:X): Not defined: scoring uses the Base Attack Complexity (AC).
Modified attack requirements (MAT:X): Not defined: scoring uses the Base Attack Requirements (AT).
Modified privileges required (MPR:X): Not defined: scoring uses the Base Privileges Required (PR).
Modified user interaction (MUI:X): Not defined: scoring uses the Base User Interaction (UI).
Modified vulnerable system confidentiality impact (MVC:X): Not defined: scoring uses the Base VC metric.
Modified vulnerable system integrity impact (MVI:X): Not defined: scoring uses the Base VI metric.
Modified vulnerable system availability impact (MVA:X): Not defined: scoring uses the Base VA metric.
Modified subsequent system confidentiality impact (MSC:X): Not defined: scoring uses the Base SC metric.
Modified subsequent system integrity impact (MSI:X): Not defined: scoring uses the Base SI metric.
Modified subsequent system availability impact (MSA:X): Not defined: scoring uses the Base SA metric.
Safety (supplemental) (S:X): Not evaluated.
Automatable (supplemental) (AU:X): Not evaluated.
Recovery (supplemental) (R:X): Not evaluated.
Value density (supplemental) (V:X): Not evaluated.
Vulnerability response effort (supplemental) (RE:X): Not evaluated.
Provider urgency (supplemental) (U:X): Not evaluated.

—

[email protected]

5.5

3.1

MEDIUM

CVSS:3.1/AV:L/AC:L/PR:N/UI:R/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:N): No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R): A real person has to do something—click, install, enable—otherwise it doesn’t land.
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-2026-24116

vendor	priority	summary	link
`debian`	unimportant	CVE-2026-24116 unimportant 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-2026-24116
`ubuntu`	medium	CVE-2026-24116 medium priority: Ubuntu including 1 source packages (rust-wasmtime), 4 status rows across 4 suites (jammy, noble, questing, upstream): needs-triage 3, DNE 1.	https://ubuntu.com/security/CVE-2026-24116

Affected software / configurations for CVE-2026-24116

Vendor	Product	Version	Raw CPE
bytecodealliance	wasmtime	>= 29.0.0, < 36.0.5	cpe:2.3:a:bytecodealliance:wasmtime::::::rust::*
bytecodealliance	wasmtime	>= 40.0.0, < 40.0.3	cpe:2.3:a:bytecodealliance:wasmtime::::::rust::*
bytecodealliance	wasmtime	>= 41.0.0, < 41.0.1	cpe:2.3:a:bytecodealliance:wasmtime::::::rust::*

References for CVE-2026-24116

URL	Tags
https://docs.rs/wasmtime/latest/wasmtime/struct.Config.html#method.memory_guard_size	Product
https://docs.rs/wasmtime/latest/wasmtime/struct.Config.html#method.signals_based_traps	Product
https://docs.wasmtime.dev/stability-release.html	Release Notes
https://github.com/bytecodealliance/wasmtime/commit/728fa07184f8da2a046f48ef9b61f869dce133a6	Patch
https://github.com/bytecodealliance/wasmtime/commit/799585fc362fcb991de147dd1a9f2ba0861ed440	Patch
https://github.com/bytecodealliance/wasmtime/commit/ac92d9bb729ad3a6d93f0724c4c33a0c4a9c0227	Patch
https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-vc8c-j3xm-xj73	Patch Vendor Advisory
https://rustsec.org/advisories/RUSTSEC-2026-0006.html	Third Party Advisory

URL

CVE-2026-24116 | Wasmtime segfault or unused out-of-sandbox load with f64.copysign operator on x86-64

Exploit prediction scoring system (EPSS) score for CVE-2026-24116

Common vulnerability scoring system (CVSS) metrics for CVE-2026-24116

Weakness enumeration for CVE-2026-24116

GitHub Security Advisory for CVE-2026-24116

OS Trackers for CVE-2026-24116

Affected software / configurations for CVE-2026-24116

References for CVE-2026-24116