CVE-2026-34943

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Prior to 24.0.7, 36.0.7, 42.0.2, and 43.0.1, Wasmtime contains a possible panic which can happen when a flags-typed component model value is lifted with the Val type. If bits are set outside of the set of flags the component model specifies that these bits should be ignored but Wasmtime will panic when this value is lifted. This panic only affects wasmtime's implementation of lifting into Val, not when using the flags! macro. This additionally only affects flags-typed values which are part of a WIT interface. This has the risk of being a guest-controlled panic within the host which Wasmtime considers a DoS vector. This vulnerability is fixed in 24.0.7, 36.0.7, 42.0.2, and 43.0.1."}, {"lang": "es", "value": "Wasmtime es un runtime para WebAssembly. Antes de 24.0.7, 36.0.7, 42.0.2 y 43.0.1, Wasmtime contiene un posible p\u00e1nico que puede ocurrir cuando un valor de modelo de componente de tipo \u2019flags\u2019 es elevado con el tipo Val. Si los bits se establecen fuera del conjunto de \u2019flags\u2019, el modelo de componente especifica que estos bits deben ser ignorados, pero Wasmtime entrar\u00e1 en p\u00e1nico cuando este valor sea elevado. Este p\u00e1nico solo afecta la implementaci\u00f3n de Wasmtime de la elevaci\u00f3n a Val, no cuando se usa la macro \u2019flags!\u2019. Esto adicionalmente solo afecta a los valores de tipo \u2019flags\u2019 que forman parte de una interfaz WIT. Esto tiene el riesgo de ser un p\u00e1nico controlado por el invitado dentro del anfitri\u00f3n que Wasmtime considera un vector de DoS. Esta vulnerabilidad est\u00e1 corregida en 24.0.7, 36.0.7, 42.0.2 y 43.0.1."}], "id": "CVE-2026-34943", "lastModified": "2026-10-26T21:10:00.170", "metrics": {"cvssMetricV31": [{"cvssData": {"attackComplexity": "LOW", "attackVector": "NETWORK", "availabilityImpact": "HIGH", "baseScore": 7.5, "baseSeverity": "HIGH", "confidentialityImpact": "NONE", "integrityImpact": "NONE", "privilegesRequired": "NONE", "scope": "UNCHANGED", "userInteraction": "NONE", "vectorString": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H", "version": "3.1"}, "exploitabilityScore": 3.9, "impactScore": 3.6, "source": "nvd@nist.gov", "type": "Primary"}], "cvssMetricV40": [{"cvssData": {"Automatable": "NOT_DEFINED", "Recovery": "NOT_DEFINED", "Safety": "NOT_DEFINED", "attackComplexity": "HIGH", "attackRequirements": "PRESENT", "attackVector": "NETWORK", "availabilityRequirement": "NOT_DEFINED", "baseScore": 5.6, "baseSeverity": "MEDIUM", "confidentialityRequirement": "NOT_DEFINED", "exploitMaturity": "NOT_DEFINED", "integrityRequirement": "NOT_DEFINED", "modifiedAttackComplexity": "NOT_DEFINED", "modifiedAttackRequirements": "NOT_DEFINED", "modifiedAttackVector": "NOT_DEFINED", "modifiedPrivilegesRequired": "NOT_DEFINED", "modifiedSubAvailabilityImpact": "NOT_DEFINED", "modifiedSubConfidentialityImpact": "NOT_DEFINED", "modifiedSubIntegrityImpact": "NOT_DEFINED", "modifiedUserInteraction": "NOT_DEFINED", "modifiedVulnAvailabilityImpact": "NOT_DEFINED", "modifiedVulnConfidentialityImpact": "NOT_DEFINED", "modifiedVulnIntegrityImpact": "NOT_DEFINED", "privilegesRequired": "HIGH", "providerUrgency": "NOT_DEFINED", "subAvailabilityImpact": "NONE", "subConfidentialityImpact": "NONE", "subIntegrityImpact": "NONE", "userInteraction": "ACTIVE", "valueDensity": "NOT_DEFINED", "vectorString": "CVSS:4.0/AV:N/AC:H/AT:P/PR:H/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", "version": "4.0", "vulnAvailabilityImpact": "HIGH", "vulnConfidentialityImpact": "NONE", "vulnIntegrityImpact": "NONE", "vulnerabilityResponseEffort": "NOT_DEFINED"}, "source": "security-advisories@github.com", "type": "Secondary"}], "ssvcV203": [{"source": "134c704f-9b21-4f2e-91b3-4a467353bcc0", "ssvcData": {"id": "CVE-2026-34943", "options": [{"exploitation": "none"}, {"automatable": "yes"}, {"technicalImpact": "partial"}], "role": "CISA Coordinator", "timestamp": "2026-04-13T20:15:13.926993Z", "version": "2.0.3"}}]}, "published": "2026-04-09T19:16:24.020", "references": [{"source": "security-advisories@github.com", "tags": ["Vendor Advisory"], "url": "https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-m758-wjhj-p3jq"}], "sourceIdentifier": "security-advisories@github.com", "vulnStatus": "Analyzed", "weaknesses": [{"description": [{"lang": "en", "value": "CWE-248"}], "source": "security-advisories@github.com", "type": "Secondary"}]}

{"bugzilla": {"description": "Wasmtime: Wasmtime: Denial of Service due to malformed flags-typed component model value processing", "id": "2457005", "url": "https://bugzilla.redhat.com/show_bug.cgi?id=2457005"}, "csaw": false, "cvss3": {"cvss3_base_score": "5.0", "cvss3_scoring_vector": "CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:N/I:N/A:L", "status": "draft"}, "cwe": "CWE-1287", "details": ["A flaw was found in Wasmtime, a runtime for WebAssembly. A malicious guest can exploit an issue where a flags-typed component model value, containing unexpected bit settings, causes the host system to panic during processing. This vulnerability can lead to a Denial of Service (DoS), rendering the host system unresponsive."], "mitigation": {"lang": "en:us", "value": "Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability."}, "name": "CVE-2026-34943", "package_state": [{"cpe": "cpe:/a:redhat:connectivity_link:1", "fix_state": "Fix deferred", "package_name": "redhat-user-workloads/rhcl-1-3-wasm-shim", "product_name": "Red Hat Connectivity Link 1"}, {"cpe": "cpe:/o:redhat:enterprise_linux:10", "fix_state": "Fix deferred", "package_name": "virt-firmware-rs", "product_name": "Red Hat Enterprise Linux 10"}], "public_date": "2026-04-09T18:36:51Z", "references": ["https://www.cve.org/CVERecord?id=CVE-2026-34943\nhttps://nvd.nist.gov/vuln/detail/CVE-2026-34943\nhttps://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-m758-wjhj-p3jq"], "threat_severity": "Moderate"}

{"affected": [{"configurations": [{"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[0,24.0.7)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[25.0.0,36.0.7)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[37.0.0,42.0.2)"}}, {"platform": null, "status": "affected", "versions": {"scheme": "semver", "value": "[43.0.0,44.0.1)"}}], "enrichment": {"confidence": 100.0, "confidence_source": "matching", "scores": [{"score": 100.0, "source": "matching"}]}, "original": {"product": "wasmtime", "source": "cna", "vendor": "bytecodealliance"}, "product": "wasmtime", "vendor": "bytecodealliance"}], "analysis": {"en": {"generated_at": "2026-04-10T02:26:04.514631+00:00", "value": {"mitigation_remediation": ["Upgrade Wasmtime to at least version 24.0.7, 36.0.7, 42.0.2, or 43.0.1, depending on the release line in use."], "summary": {"action": "Immediate Patch", "impact": "Denial of Service resulting from host crash"}, "threat_synthesis": {"affected_systems": "The vulnerability affects the Wasmtime runtime from Bytecode Alliance. All releases earlier than 24.0.7 on the 24.x line, earlier than 36.0.7 on the 36.x line, earlier than 42.0.2 on the 42.x line, and earlier than 43.0.1 on the 43.x line are susceptible. Organizations that embed Wasmtime in their applications or infrastructure must verify which version they are using and ensure it is later than the noted patches.", "description_and_impact": "Wasmtime converts WebAssembly component values into internal Val objects. In releases before 24.0.7, 36.0.7, 42.0.2 and 43.0.1, an attempt to lift a flags\u2011typed component value that contains bits outside the allowed flag set triggers a panic during the lift process. The panic causes the host runtime to crash, which can be induced by a guest WebAssembly module that supplies a crafted flags value. This failure mode is an unhandled panic, not a silent error, and therefore the host terminates execution, resulting in a denial of service for any service running the affected Wasmtime instance.", "risk_and_exploitability": "The CVSS score of 5.6 classifies this issue as medium severity. EPSS data is not available, and the vulnerability is not listed in the CISA Known Exploited Vulnerabilities catalog, indicating no known widespread exploitation yet. Nevertheless, the flaw can be triggered by any untrusted WebAssembly module supplying a malicious flags\u2011typed component value, implying that an attacker who controls guest code can induce a host crash. The risk to environments exposed to untrusted code is therefore significant, even though the exploit difficulty and potential for widespread impact are moderate. Updating to a patched release removes this risk."}}}}, "created": "2026-04-10T08:39:18.066264+00:00", "updated": "2026-04-10T09:31:42.035660+00:00", "vendors": ["bytecodealliance", "bytecodealliance$PRODUCT$wasmtime"]}