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CVE-2026-34987

Wasmtime is a runtime for WebAssembly. From 25.0.0 to before 36.0.7, 42.0.2, and 43.0.1, Wasmtime with its Winch (baseline) non-default compiler backend may allow properly constructed guest Wasm to access host memory outside of its linear-memory sandbox. This vulnerability requires use of the Winch compiler (-Ccompiler=winch). By default, Wasmtime uses its Cranelift backend, not Winch. With Winch, the same incorrect assumption is present in theory on both aarch64 and x86-64. The aarch64 case has
Lifecycle PUBLISHED1 preserved revisionFact urn:baitaphish:canonical-cve-fact-revision:v2:be5bd64b689626f24af8637f7e86c2983c03fb4da77c5d462d70f3a41e551f05
Known exploited
Not asserted
Disputed
No
Stale source
No
Conflicts
1

Preserved source conflicts

No provider value was silently selected as the winner.

cwe · 2 assertions

{"cweId":"CWE-125","description":"CWE-125: Out-of-bounds Read","lang":"en","type":"CWE"}

  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:0f73d4d580ee0d7c25d41f052781507d3dfaafd8d723c1cbc23ec66beb701a46 · sha256:2c5f49b61c7cbdfa… · /containers/cna/problemTypes/0/descriptions/0

{"cweId":"CWE-787","description":"CWE-787: Out-of-bounds Write","lang":"en","type":"CWE"}

  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:0f73d4d580ee0d7c25d41f052781507d3dfaafd8d723c1cbc23ec66beb701a46 · sha256:2c5f49b61c7cbdfa… · /containers/cna/problemTypes/1/descriptions/0

Affected products and versions

1 source assertion
{"product":"wasmtime","vendor":"bytecodealliance","versions":[{"status":"affected","version":">= 25.0.0, < 36.0.7"},{"status":"affected","version":">= 37.0.0, < 42.0.2"},{"status":"affected","version":">= 43.0.0, < 44.0.1"}]}
  • cve_program_cvelist_v5affected
    urn:baitaphish:normalized-source-record:v2:0f73d4d580ee0d7c25d41f052781507d3dfaafd8d723c1cbc23ec66beb701a46 · sha256:2c5f49b61c7cbdfa… · /containers/cna/affected/0

Provider-owned CVSS observations

1 source assertion
{"metric":{"attackComplexity":"LOW","attackRequirements":"PRESENT","attackVector":"NETWORK","baseScore":9,"baseSeverity":"CRITICAL","privilegesRequired":"LOW","subAvailabilityImpact":"HIGH","subConfidentialityImpact":"HIGH","subIntegrityImpact":"HIGH","userInteraction":"NONE","vectorString":"CVSS:4.0/AV:N/AC:L/AT:P/PR:L/UI:N/VC:H/VI:H/VA:H/SC:H/SI:H/SA:H","version":"4.0","vulnAvailabilityImpact":"HIGH","vulnConfidentialityImpact":"HIGH","vulnIntegrityImpact":"HIGH"},"metric_type":"cvssV4_0"}
  • cve_program_cvelist_v5cvss
    urn:baitaphish:normalized-source-record:v2:0f73d4d580ee0d7c25d41f052781507d3dfaafd8d723c1cbc23ec66beb701a46 · sha256:2c5f49b61c7cbdfa… · /containers/cna/metrics/0/cvssV4_0

CWE assertions

2 source assertions
{"cweId":"CWE-125","description":"CWE-125: Out-of-bounds Read","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:0f73d4d580ee0d7c25d41f052781507d3dfaafd8d723c1cbc23ec66beb701a46 · sha256:2c5f49b61c7cbdfa… · /containers/cna/problemTypes/0/descriptions/0
{"cweId":"CWE-787","description":"CWE-787: Out-of-bounds Write","lang":"en","type":"CWE"}
  • cve_program_cvelist_v5cwe
    urn:baitaphish:normalized-source-record:v2:0f73d4d580ee0d7c25d41f052781507d3dfaafd8d723c1cbc23ec66beb701a46 · sha256:2c5f49b61c7cbdfa… · /containers/cna/problemTypes/1/descriptions/0

Source references

1 source assertion
{"name":"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xx5w-cvp6-jv83","tags":["x_refsource_CONFIRM"],"url":"https://github.com/bytecodealliance/wasmtime/security/advisories/GHSA-xx5w-cvp6-jv83"}
  • cve_program_cvelist_v5reference
    urn:baitaphish:normalized-source-record:v2:0f73d4d580ee0d7c25d41f052781507d3dfaafd8d723c1cbc23ec66beb701a46 · sha256:2c5f49b61c7cbdfa… · /containers/cna/references/0

Attribution and limitations

  • CVE Program CVEList V5: Reproduce the MITRE copyright designation and CVE license in copies. Source →

Provider severity values are preserved separately. Baitaphish does not convert them into a risk rating, infer affected products, or treat EPSS as observed exploitation.

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