{"answers":{"affected":"1 open source package ship an affected version, including msgpack.","exploited":"There is no known exploitation of CVE-2026-126366 in the wild and no public exploit code.","exposure":"An affected version is only exploitable if your software calls MessagePack.unpack or MessagePack::Unpacker. Many projects that include it are not exposed.","fix":"Upgrade msgpack to 1.8.7 or later.","what":"CVE-2026-126366 is a high-severity denial of service vulnerability in msgpack-ruby, published on 12 Nov 2026. An attacker can exploit it over the internet without logging in, with no action from the victim."},"fix_prompt":"Check this codebase for CVE-2026-126366 and fix it if it is affected.\n\nWhat it is: CVE-2026-126366 is a high-severity denial of service vulnerability in msgpack-ruby, published on 12 Nov 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.\nExploitation: There is no known exploitation of CVE-2026-126366 in the wild and no public exploit code.\nExposure: An affected version is only exploitable if your software calls MessagePack.unpack or MessagePack::Unpacker. Many projects that include it are not exposed.\n\nAffected packages and fixed versions:\n- msgpack (RubyGems): affected all versions; fixed in 1.8.7\n\nTask:\n1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.\n   If an affected version is present, also search the code for calls to MessagePack.unpack or MessagePack::Unpacker and report whether any exist.\n2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.\n3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.\n4. Run the tests and summarise what changed and why.\n5. If nothing in the project is affected, say so and change nothing.\n\nReference: https://insights.sbomify.com/CVE-2026-126366/ (Markdown: https://insights.sbomify.com/CVE-2026-126366/index.md)","id":"CVE-2026-126366","markdown":"https://insights.sbomify.com/CVE-2026-126366/index.md","name":"CVE-2026-126366","record":{"aliases":["GHSA-73v3-wf97-vpgj"],"analysis":{"component_type":"library","exploitable_when_present":false,"fix_type":"upgrade","impacts":["denial_of_service"],"network_reachable":"yes","non_default_config":false,"product_category":"Ruby serialization library","requires_auth":"none","requires_specific_call":true,"summary":"Attackers sending short MessagePack headers can force huge allocations and exhaust the JVM heap in apps decoding untrusted input with msgpack-java.","user_interaction":"not_required","vuln_class":"denial_of_service","vulnerable_functions":["MessagePack.unpack","MessagePack::Unpacker"]},"analysis_generated_by":"sbomify/insights-2b-fp8","assigner":"GitHub_M","cpe":[],"cvss":{"score":7.5,"severity":"high","source":"cna","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H","version":"3.1"},"cwes":[{"id":"CWE-770","name":"Allocation of Resources Without Limits or Throttling"},{"id":"CWE-1325","name":"Improperly Controlled Sequential Memory Allocation"}],"description":"MessagePack for Ruby is an implementation of the MessagePack binary serialization format. Prior to 1.8.7, the Java-platform msgpack gem for JRuby allocated arrays and byte buffers directly from attacker-controlled array32, str32, and bin32 declared sizes before confirming that corresponding elements or bytes were available. A short MessagePack header could therefore trigger a very large allocation or sustained heap growth when an application decoded untrusted input through MessagePack.unpack or MessagePack::Unpacker, potentially exhausting the shared JVM heap. map32 and declared counts at or above 2^31 did not use the affected allocation behavior. This issue is fixed in version 1.8.7.","ecosystems":["RubyGems"],"exploits":{"exploitdb":0,"first_seen":null,"github_poc":0,"max_poc_stars":null,"metasploit":0,"nuclei":0,"refs":[],"tier":"none_known"},"has_fix":true,"headline":"msgpack-java JRuby decoder allocates from declared header counts with no cap: 5-byte message forces multi-GiB OOM","id":"CVE-2026-126366","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"RubyGems","product":null,"products":[],"type":"denial_of_service","year":"2026"},"n_packages":1,"n_references":4,"next":{"headline":"@grpc/grpc-js: safe_regex incorrectly applies partial string matching for patterns with alternation","id":"CVE-2026-126367"},"nickname":null,"packages":[{"ecosystem":"RubyGems","fixed":["1.8.7"],"introduced":["0"],"last_affected":[],"package":"msgpack","purl":null,"source":"GHSA-73v3-wf97-vpgj"}],"prev":{"headline":"Astro: XSS via unescaped code for unsupported languages in @astrojs/prism","id":"CVE-2026-126365"},"products":["msgpack-ruby"],"published":"2026-11-12","related":[],"sources":[{"class":"attribution","licence":"CVE Terms of Use (MITRE)","name":"CVE List","prefix":"CVE"},{"class":"attribution","licence":"CC BY 4.0","name":"GitHub Advisory Database","prefix":"GHSA"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":null,"exploitation":null,"technical_impact":null},"state":"PUBLISHED","updated":"2026-11-12","vendors":["msgpack"]},"summary":"Attackers sending short MessagePack headers can force huge allocations and exhaust the JVM heap in apps decoding untrusted input with msgpack-java.","url":"https://insights.sbomify.com/CVE-2026-126366/"}