{"answers":{"affected":"4 open source packages ship an affected version, including MessagePack. It affects 1 product.","exploited":"There is no known exploitation of CVE-2026-48509 in the wild and no public exploit code.","fix":"Upgrade MessagePack to a fixed version for your release line: 2.5.301 or 3.1.7.","what":"CVE-2026-48509 is a medium-severity denial of service vulnerability in MessagePack-CSharp, published on 22 Jun 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-2026-48509 and fix it if it is affected.\n\nWhat it is: CVE-2026-48509 is a medium-severity denial of service vulnerability in MessagePack-CSharp, published on 22 Jun 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-2026-48509 in the wild and no public exploit code.\n\nAffected packages and fixed versions:\n- MessagePack (NuGet): affected all versions; fixed in 2.5.301\n- MessagePack (NuGet): affected all versions; fixed in 2.5.301\n- MessagePack (NuGet): affected from 3.0; fixed in 3.1.7\n- MessagePack (NuGet): affected from 3.0; fixed in 3.1.7\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.\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-2026-48509/ (Markdown: https://insights.sbomify.com/CVE-2026-48509/index.md)","id":"CVE-2026-48509","markdown":"https://insights.sbomify.com/CVE-2026-48509/index.md","name":"CVE-2026-48509","record":{"aliases":["ECHO-e60c-e8f0-b786","GHSA-2f33-pr97-265q"],"analysis":{"component_type":"library","fix_type":"upgrade","impacts":["denial_of_service"],"network_reachable":"yes","non_default_config":false,"product_category":"C# MessagePack library","requires_auth":"none","summary":"Insecure default security settings in MessagePack-CSharp allow attackers to cause denial of service via hash-collision attacks on ASP.NET Core request bodies.","user_interaction":"not_required","vuln_class":"denial_of_service"},"analysis_generated_by":"qwen3.8-flash-next","assigner":"GitHub_M","cpe":[{"product":"messagepack","vendor":"messagepack"}],"cvss":{"score":6.3,"severity":"medium","source":"cna","vector":"CVSS:4.0/AV:N/AC:H/AT:P/PR:N/UI:N/VC:N/VI:L/VA:L/SC:N/SI:N/SA:N","version":"4.0"},"cwes":[{"id":"CWE-1188","name":"Initialization of a Resource with an Insecure Default"}],"description":"MessagePack for C# is a MessagePack serializer for C#. Prior to 2.5.301 and 3.1.7, the parameterless MessagePackInputFormatter() constructor uses default serializer options, which resolve to MessagePackSerializerOptions.Standard with MessagePackSecurity.TrustedData. The formatter is designed for ASP.NET Core MVC request bodies, which commonly cross an HTTP trust boundary. This insecure default can expose applications to denial-of-service attacks that MessagePackSecurity.UntrustedData is intended to mitigate, such as hash-collision attacks against dictionary-like model properties. This vulnerability is fixed in 2.5.301 and 3.1.7.","ecosystems":["NuGet"],"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":"MessagePack-CSharp: ASP.NET Core MessagePackInputFormatter defaults to TrustedData for HTTP request bodies","id":"CVE-2026-48509","indexable":true,"kev":null,"kind":"cve","links":{"ecosystem":"NuGet","product":null,"products":[],"type":"denial_of_service","year":"2026"},"n_packages":4,"n_references":1,"next":{"headline":"MessagePack-CSharp: LZ4 decompression allocates from unbounded declared output lengths","id":"CVE-2026-48510"},"packages":[{"ecosystem":"NuGet","fixed":["2.5.301"],"introduced":["0"],"last_affected":[],"package":"MessagePack","purl":null,"source":"GHSA-2f33-pr97-265q"},{"ecosystem":"NuGet","fixed":["2.5.301"],"introduced":["0"],"last_affected":[],"package":"MessagePack","purl":"pkg:nuget/MessagePack","source":"GHSA-2f33-pr97-265q"},{"ecosystem":"NuGet","fixed":["3.1.7"],"introduced":["3.0"],"last_affected":[],"package":"MessagePack","purl":null,"source":"GHSA-2f33-pr97-265q"},{"ecosystem":"NuGet","fixed":["3.1.7"],"introduced":["3.0"],"last_affected":[],"package":"MessagePack","purl":"pkg:nuget/MessagePack","source":"GHSA-2f33-pr97-265q"}],"prev":{"headline":"Lemur: Authorization bypass in StrictRolePermission / AuthorityCreatorPermission","id":"CVE-2026-48508"},"products":["MessagePack-CSharp"],"published":"2026-06-22","related":[{"cvss_score":8.2,"headline":"MessagePack-CSharp: LZ4 decompression may fail with AccessViolationException after dereferencing memory from bad input","id":"CVE-2026-48109","kev_date_added":null,"published":"2026-06-22"},{"cvss_score":8.2,"headline":"MessagePack-CSharp: Denial of service vulnerabilities can swamp the CPU or crash the process with stack and heap overflows","id":"CVE-2026-48502","kev_date_added":null,"published":"2026-06-22"},{"cvss_score":7.5,"headline":"MessagePack-CSharp: MessagePackReader.Skip can recurse without enforcing maximum object graph depth","id":"CVE-2026-48506","kev_date_added":null,"published":"2026-06-22"},{"cvss_score":6.3,"headline":"MessagePack-CSharp: LZ4 decompression allocates from unbounded declared output lengths","id":"CVE-2026-48510","kev_date_added":null,"published":"2026-06-22"},{"cvss_score":6.3,"headline":"MessagePack-CSharp: ExpandoObject formatter can perform quadratic insertion work on untrusted maps","id":"CVE-2026-48511","kev_date_added":null,"published":"2026-06-22"},{"cvss_score":6.3,"headline":"MessagePack-CSharp: JSON conversion APIs can recurse without consistent depth enforcement","id":"CVE-2026-48512","kev_date_added":null,"published":"2026-06-22"}],"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":"US public information, NVD API terms","name":"NVD"},{"class":"attribution","licence":"CWE Terms of Use","name":"CWE (MITRE)"},{"class":"attribution","licence":"FIRST CVSS licence","name":"CVSS (FIRST)"}],"ssvc":{"automatable":"no","exploitation":"none","technical_impact":"partial"},"state":"PUBLISHED","updated":"2026-06-25","vendors":["MessagePack-CSharp"]},"summary":"Insecure default security settings in MessagePack-CSharp allow attackers to cause denial of service via hash-collision attacks on ASP.NET Core request bodies.","url":"https://insights.sbomify.com/CVE-2026-48509/"}