CVE-2026-55407

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.

CVSS 4.0

6.3CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/SC:N/SI:N/SA:N

EPSS

0.8% chance of exploitation in the next 30 days; higher than 54% of CVEs (scores of 2026-10-25)

CWEs

CWE-400, CWE-770, CWE-789

Published

2026-07-16

Modified

2026-10-24

Record from

the NVD, synced 2026-10-25

Packages (OSV)

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

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