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Vulnerability · Published Jul 16, 2026 · Assigned by GitHub_M

CVE-2026-55407Buffa: Memory Exhaustion Denial of Service in decode_unknown_field via Unbounded Allocation

Medium 6.3

In plain English

A medium-severity uncontrolled resource consumption in buffa from anthropics. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.8% (higher than 55% of all known vulnerabilities).

Severity (CVSS 4.0)6.3Medium
Exploit odds (30 days)0.8%top 44.7% of all CVEs
Exploited in the wildNo reportsCISA SSVC: none
Attack toolingNoneno public tooling known

Official 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.

Affected products (as reported)

VendorProductVersions
anthropics buffa < 0.8.0

Weakness: CWE-400, CWE-770, CWE-789 · 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

References