{"id":"CVE-2026-55407","revision":null,"records":[{"revision":"b216d24b34de4509bca2336f6ad671ef","observedAt":"2026-10-23T15:48:27.903+00:00","statement":{"source":"cve-program","id":"CVE-2026-55407","aliases":[],"title":"Buffa: Memory Exhaustion Denial of Service in decode_unknown_field via Unbounded Allocation","description":"Buffa is a pure-Rust Protocol Buffers implementation with first-class protobuf editions support. Prior to 0.8.0, the decode_unknown_field function in buffa's protobuf decoder allocated heap memory in proportion to untrusted input (unknown fields in the serialized protobuf) without enforcing an allocation budget, affecting any message decoded from untrusted input using code generated with preserve_unknown_fields=true (the default); a small, well-formed payload of nested unknown fields inside a StartGroup could trigger roughly 22x memory amplification (for example a 64 MiB input forcing about 1.4 GB of heap allocation), and length-delimited unknown fields could be sized arbitrarily, so an unauthenticated attacker could crash a process through memory exhaustion because the top-level message size cap did not account for in-decode amplification. This issue is fixed in version 0.8.0.","state":0,"publishedAt":"2026-07-16T15:57:31.704+00:00","modifiedAt":"2026-07-16T18:04:39.764+00:00","affected":[{"ecosystem":"Vendor product","name":"buffa","ranges":[],"versions":[],"rawVersionEvidence":"{\n                    \"vendor\": \"anthropics\",\n                    \"product\": \"buffa\",\n                    \"versions\": [\n                        {\n                            \"version\": \"< 0.8.0\",\n                            \"status\": \"affected\"\n                        }\n                    ]\n                }"}],"metrics":[{"system":"CVSS 4.0","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N","score":6.3,"severity":"MEDIUM"}],"references":["https://github.com/anthropics/buffa/security/advisories/GHSA-f9qc-qg88-7pq5","https://github.com/anthropics/buffa/pull/184","https://github.com/anthropics/buffa/commit/278fa43fcff661d4ee6bd83b75955a153d4281fc","https://github.com/anthropics/buffa/releases/tag/v0.8.0"],"sourceUrl":"https://www.cve.org/CVERecord?id=CVE-2026-55407","license":"CVE Program Terms of Use","key":"cve-program:CVE-2026-55407","identifiers":["CVE-2026-55407"]},"retained":false,"historicalAffected":[]},{"revision":"0830c18caff0401485cdef19677804ba","observedAt":"2026-10-25T13:17:34.255+00:00","statement":{"source":"nvd","id":"CVE-2026-55407","aliases":[],"title":"Buffa is a pure-Rust Protocol Buffers implementation with first-class protobuf editions support. Prior to 0.8.0, the decode_unknown_field function in buffa's protobuf decoder allocated heap memory in proportion to untrusted input (unknown f…","description":"Buffa is a pure-Rust Protocol Buffers implementation with first-class protobuf editions support. Prior to 0.8.0, the decode_unknown_field function in buffa's protobuf decoder allocated heap memory in proportion to untrusted input (unknown fields in the serialized protobuf) without enforcing an allocation budget, affecting any message decoded from untrusted input using code generated with preserve_unknown_fields=true (the default); a small, well-formed payload of nested unknown fields inside a StartGroup could trigger roughly 22x memory amplification (for example a 64 MiB input forcing about 1.4 GB of heap allocation), and length-delimited unknown fields could be sized arbitrarily, so an unauthenticated attacker could crash a process through memory exhaustion because the top-level message size cap did not account for in-decode amplification. This issue is fixed in version 0.8.0.","state":0,"publishedAt":"2026-07-16T17:16:57.77+00:00","modifiedAt":"2026-10-24T20:10:00.137+00:00","affected":[],"metrics":[{"system":"CVSS 4.0 · security-advisories@github.com · Secondary","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/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","score":6.3,"severity":"MEDIUM"}],"references":["https://github.com/anthropics/buffa/commit/278fa43fcff661d4ee6bd83b75955a153d4281fc","https://github.com/anthropics/buffa/pull/184","https://github.com/anthropics/buffa/releases/tag/v0.8.0","https://github.com/anthropics/buffa/security/advisories/GHSA-f9qc-qg88-7pq5"],"sourceUrl":"https://nvd.nist.gov/vuln/detail/CVE-2026-55407","license":"NIST NVD usage terms; underlying source attribution retained","enrichment":{"sourceStatus":"Deferred","weaknesses":["CWE-400","CWE-770","CWE-789"],"productCriteria":[],"sourceDates":{"published":"2026-07-16T17:16:57.770","lastModified":"2026-10-24T20:10:00.137"},"relatedAdvisories":[],"note":"NVD analysis and CPE criteria are source context, not proof that a package or your environment is affected. Complete affected data, logical configurations and SSVC are retained in the original JSON."},"key":"nvd:CVE-2026-55407","identifiers":["CVE-2026-55407"]},"retained":false,"historicalAffected":[]},{"revision":"4c36920c440040699b05c326dcc1bc60","observedAt":"2026-10-24T13:19:54.901+00:00","statement":{"source":"osv","id":"GHSA-f9qc-qg88-7pq5","aliases":["CVE-2026-55407"],"title":"Buffa Vulnerable to Memory Exhaustion Denial of Service in decode_unknown_field via Unbounded Allocation","description":"The `decode_unknown_field` function in buffa's protobuf decoder allocated heap memory in proportion to untrusted input (unknown fields in the serialized protobuf) without enforcing an allocation budget. Any message decoded from untrusted input using code generated with `preserve_unknown_fields=true` (the default) was affected. A small, well-formed payload of nested unknown fields inside a StartGroup could trigger roughly 22× memory amplification (e.g., a 64 MiB input forcing ~1.4 GB of heap allocation), and length-delimited unknown fields could be sized arbitrarily, enabling an unauthenticated attacker to crash a process via memory exhaustion. This was reachable from the default decode APIs, since the top-level message size cap did not account for in-decode amplification. \n\nFor users of connectrpc - the DEFAULT_MAX_MESSAGE_SIZE for connectrpc is 4MiB, which limits amplification in the worst case to ~88 MiB of memory. A flood of concurrent requests with this pattern could still be used to exhaust available memory, however.\n\nUsers are advised to either set `preserve_unknown_fields=false` on their current generated code, or upgrade to 0.8.0, which enforces per-message unknown field count limits - this is configurable, with a default of 1 million unknown fields, or ~40MiB of allocation overhead per message.\nUsers are advised to update to the latest version, which enforces per-message unknown field count limits.\n\nThank you to @p80n-sec for reporting this issue.","state":0,"publishedAt":"2026-08-28T18:34:22+00:00","modifiedAt":"2026-08-28T18:45:06.8333937+00:00","affected":[{"ecosystem":"crates.io","name":"buffa","ranges":[{"type":"SEMVER","events":[{"kind":"introduced","version":"0"},{"kind":"fixed","version":"0.8.0"}]}],"versions":[],"rawVersionEvidence":null}],"metrics":[{"system":"CVSS_V4","vector":"CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N","score":null,"severity":null},{"system":"Publisher rating","vector":null,"score":null,"severity":"MODERATE"}],"references":["https://github.com/anthropics/buffa/security/advisories/GHSA-f9qc-qg88-7pq5","https://nvd.nist.gov/vuln/detail/CVE-2026-55407","https://github.com/anthropics/buffa/pull/184","https://github.com/anthropics/buffa/commit/278fa43fcff661d4ee6bd83b75955a153d4281fc","https://github.com/anthropics/buffa","https://github.com/anthropics/buffa/releases/tag/v0.8.0"],"sourceUrl":"https://github.com/advisories/GHSA-f9qc-qg88-7pq5","license":"GitHub Advisory Database · CC-BY-4.0","key":"osv:GHSA-f9qc-qg88-7pq5","identifiers":["GHSA-f9qc-qg88-7pq5","CVE-2026-55407"]},"retained":false,"historicalAffected":[]}],"coverage":[{"source":"cisa-kev:global","scope":"Complete CISA KEV catalog; all vendors. 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