{"id":"GHSA-6wgr-89rj-399p","revision":null,"records":[{"revision":"ab04d1052a464ba3802b7554aecd0ef3","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-34988","aliases":[],"title":"Wasmtime leaks data between pooling allocator instances","description":"Wasmtime is a runtime for WebAssembly. From 28.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime's implementation of its pooling allocator contains a bug where in certain configurations the contents of linear memory can be leaked from one instance to the next. The implementation of resetting the virtual memory permissions for linear memory used the wrong predicate to determine if resetting was necessary, where the compilation process used a different predicate. This divergence meant that the pooling allocator incorrectly deduced at runtime that resetting virtual memory permissions was not necessary while compile-time determine that virtual memory could be relied upon. The pooling allocator must be in use, Config::memory_guard_size configuration option must be 0, Config::memory_reservation configuration must be less than 4GiB, and pooling allocator must be configured with max_memory_size the same as the memory_reservation value in order to exploit this vulnerability. If all of these conditions are applicable then when a linear memory is reused the VM permissions of the previous iteration are not reset. This means that the compiled code, which is assuming out-of-bounds loads will segfault, will not actually segfault and can read the previous contents of linear memory if it was previously mapped. This represents a data leakage vulnerability between guest WebAssembly instances which breaks WebAssembly's semantics and additionally breaks the sandbox that Wasmtime provides. Wasmtime is not vulnerable to this issue with its default settings, nor with the default settings of the pooling allocator, but embeddings are still allowed to configure these values to cause this vulnerability. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.","state":0,"publishedAt":"2026-04-09T18:52:26.131+00:00","modifiedAt":"2026-04-09T19:31:07.544+00:00","affected":[{"ecosystem":"Vendor product","name":"wasmtime","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"bytecodealliance\",\n                    \"product\": \"wasmtime\",\n                    \"versions\": [\n                        {\n                            \"version\": \">= 28.0.0, < 36.0.7\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \">= 37.0.0, < 42.0.2\",\n                            \"status\": \"affected\"\n                        },\n                        {\n                            \"version\": \">= 43.0.0, < 44.0.1\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 4.0","vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N","score":2.3,"severity":"LOW"}],"references":["https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-6wgr-89rj-399p"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-34988","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-34988","identifiers":["CVE-2026-34988"]},"retained":false,"historicalAffected":[]},{"revision":"d6753cff1ddf4c97aa02c229452bf29f","observedAt":"2026-11-01T06:08:03.122+00:00","statement":{"source":"euvd","id":"EUVD-2026-21033","aliases":["CVE-2026-34988","GHSA-6wgr-89rj-399p"],"title":"Wasmtime is a runtime for WebAssembly. 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The pooling allocator must be in use, Config::memory_guard_size configuration option must be 0, Config::memory_reservation configuration must be less than 4GiB, and pooling allocator must be configured with max_memory_size the same as the memory_reservation value in order to exploit this vulnerability. If all of these conditions are applicable then when a linear memory is reused the VM permissions of the previous iteration are not reset. This means that the compiled code, which is assuming out-of-bounds loads will segfault, will not actually segfault and can read the previous contents of linear memory if it was previously mapped. This represents a data leakage vulnerability between guest WebAssembly instances which breaks WebAssembly's semantics and additionally breaks the sandbox that Wasmtime provides. Wasmtime is not vulnerable to this issue with its default settings, nor with the default settings of the pooling allocator, but embeddings are still allowed to configure these values to cause this vulnerability. This vulnerability is fixed in 36.0.7, 42.0.2, and 43.0.1.","state":0,"publishedAt":null,"modifiedAt":null,"affected":[],"metrics":[{"system":"EUVD CVSS 4.0","vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:N/VC:L/VI:N/VA:N/SC:L/SI:N/SA:N","score":2.3,"severity":null}],"references":["https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-6wgr-89rj-399p"],"sourceUrl":"https://euvd.enisa.europa.eu/vulnerability/EUVD-2026-21033","license":"ENISA EUVD · source terms and attribution apply","enrichment":{"sourceStatus":null,"weaknesses":[],"productCriteria":[],"sourceDates":{"datePublished":"Apr 9, 2026, 6:52:26 PM","dateUpdated":"Apr 9, 2026, 7:31:07 PM"},"relatedAdvisories":[{"id":"openSUSE-SU-2026:20749-1","title":"Security update for tree-sitter","vulnerabilityIds":["CVE-2026-34941","CVE-2026-34942","CVE-2026-34943","CVE-2026-34944","CVE-2026-34945","CVE-2026-34946","CVE-2026-34987","CVE-2026-34988","CVE-2026-35186","CVE-2026-35195"]},{"id":"SUSE-SU-2026:21789-1","title":"Security update for tree-sitter","vulnerabilityIds":["CVE-2026-34941","CVE-2026-34942","CVE-2026-34943","CVE-2026-34944","CVE-2026-34945","CVE-2026-34946","CVE-2026-34987","CVE-2026-34988","CVE-2026-35186","CVE-2026-35195"]},{"id":"openSUSE-SU-2026:10715-1","title":"libtree-sitter0_26-0.26.8-2.1 on GA media","vulnerabilityIds":["CVE-2026-34941","CVE-2026-34943","CVE-2026-34988","CVE-2026-35186"]}],"note":"EUVD source date text has no stated timezone and is retained without inventing a UTC instant. Related bulletin membership is not an alias, common cause or applicability claim. A missing vector with a zero score is treated as unrated. Complete vendor/product and underlying source evidence remains in the original JSON."},"key":"euvd:EUVD-2026-21033","identifiers":["EUVD-2026-21033","CVE-2026-34988","GHSA-6wgr-89rj-399p"]},"retained":false,"historicalAffected":[]},{"revision":"affcb131781a49dfa9defd1eb4ef95fb","observedAt":"2026-10-27T09:03:08.102+00:00","statement":{"source":"nvd","id":"CVE-2026-34988","aliases":[],"title":"Wasmtime is a runtime for WebAssembly. From 28.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime's implementation of its pooling allocator contains a bug where in certain configurations the contents of linear memory can be leaked from one …","description":"Wasmtime is a runtime for WebAssembly. From 28.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime's implementation of its pooling allocator contains a bug where in certain configurations the contents of linear memory can be leaked from one instance to the next. The implementation of resetting the virtual memory permissions for linear memory used the wrong predicate to determine if resetting was necessary, where the compilation process used a different predicate. This divergence meant that the pooling allocator incorrectly deduced at runtime that resetting virtual memory permissions was not necessary while compile-time determine that virtual memory could be relied upon. The pooling allocator must be in use, Config::memory_guard_size configuration option must be 0, Config::memory_reservation configuration must be less than 4GiB, and pooling allocator must be configured with max_memory_size the same as the memory_reservation value in order to exploit this vulnerability. If all of these conditions are applicable then when a linear memory is reused the VM permissions of the previous iteration are not reset. This means that the compiled code, which is assuming out-of-bounds loads will segfault, will not actually segfault and can read the previous contents of linear memory if it was previously mapped. This represents a data leakage vulnerability between guest WebAssembly instances which breaks WebAssembly's semantics and additionally breaks the sandbox that Wasmtime provides. Wasmtime is not vulnerable to this issue with its default settings, nor with the default settings of the pooling allocator, but embeddings are still allowed to configure these values to cause this vulnerability. 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Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-34988","identifiers":["CVE-2026-34988"]},"retained":false,"historicalAffected":[]},{"revision":"aced6d981b1d4fb6b56708b3ce783404","observedAt":"2026-10-24T13:19:54.901+00:00","statement":{"source":"osv","id":"GHSA-6wgr-89rj-399p","aliases":["CVE-2026-34988","RUSTSEC-2026-0088"],"title":"Wasmtime has data leakage between pooling allocator instances","description":"### Impact\n\nWasmtime's implementation of its pooling allocator contains a bug where in certain configurations the contents of linear memory can be leaked from one instance to the next. The implementation of resetting the virtual memory permissions for linear memory used the wrong predicate to determine if resetting was necessary, where the compilation process used a different predicate. This divergence meant that the pooling allocator incorrectly deduced at runtime that resetting virtual memory permissions was not necessary while compile-time determine that virtual memory could be relied upon.\n\nExposing this bug requires specific configuration values to be used. If any of these configurations are not applicable then this bug does not happen:\n\n* The pooling allocator must be in use.\n* The `Config::memory_guard_size` configuration option must be 0.\n* The `Config::memory_reservation` configuration must be less than 4GiB.\n* The pooling allocator must be configured with `max_memory_size` the same as the `memory_reservation` value.\n\nIf all of these conditions are applicable then when a linear memory is reused the VM permissions of the previous iteration are not reset. This means that the compiled code, which is assuming out-of-bounds loads will segfault, will not actually segfault and can read the previous contents of linear memory if it was previously mapped.\n\nThis represents a data leakage vulnerability between guest WebAssembly instances which breaks WebAssembly's semantics and additionally breaks the sandbox that Wasmtime provides. Wasmtime is not vulnerable to this issue with its default settings, nor with the default settings of the pooling allocator, but embeddings are still allowed to configure these values to cause this vulnerability.\n\n### Patches\n\nWasmtime 36.0.7, 42.0.2, and 43.0.1 have been issued to fix this bug. Users are recommended to update to these patched versions of Wasmtime.\n\n### Workarounds\n\nAll four conditions above must be met to be vulnerable to this bug, and users can work around this bug by adjusting any of the above conditions. 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