Anthropic’s Buffa Rust Library 0

Cybersecuritynews •Abinaya • July 1, 2026

Anthropic’s Rust-based protobuf implementation, buffa, has been found vulnerable to a zero-day denial-of-service (DoS) condition caused by unbounded heap allocation on attacker-controlled input. The flaw, now tracked as CVE-2026-55407 and GHSA-f9qc-qg88-7pq5, affects buffa and connectrpc versions before 0.8.0 and has been scored as CVSS 4.0/6.3 (Moderate). However, the real-world impact can scale to High or […]

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Zero-Day DoS Vulnerability Found in Anthropic's buffa Library A zero-day memory amplification denial-of-service (DoS) vulnerability has been discovered in Anthropic's Rust-based protobuf library, buffa. Identified as CVE-2026-55407, the flaw allows attackers to exploit unbounded-allocation data flows, leading to significant memory depletion with small inputs. Endor Labs' AI-powered static application security testing (SAST) engine detected the issue, which affects any message decoded from untrusted input using the default settings. The vulnerability is linked to the decode_unknown_field function in buffa's encoding module, where the allocation size is derived directly from untrusted input. Anthropic has engaged with Endor Labs following the disclosure to assess the severity based on deployment scenarios. The vulnerability is classified as moderate with a CVSS score of 6.3. Immediate action is advised for users of the library to mitigate potential impacts. 3 sources 58

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Anthropic’s Buffa Rust Library 0

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Attack Types (1)

CVEs (1)

MITRE ATT&CK (1)