CVE-2026-32129
soroban-poseidon provides Poseidon and Poseidon2 cryptographic hash functions for Soroban smart contracts. Poseidon V1 (PoseidonSponge) accepts variable-length inputs without injective padding. When a caller provides fewer inputs than the sponge rate (inputs.len() < T - 1), unused rate positions are implicitly zero-filled. This allows trivial hash collisions: for any input vector [m1, ..., mk] hashed with a sponge of rate > k, hash([m1, ..., mk]) equals hash([m1, ..., mk, 0]) because both produce identical pre-permutation states. This affects any use of PoseidonSponge or poseidon_hash where the number of inputs is less than T - 1 (e.g., hashing 1 input with T=3). Poseidon2 (Poseidon2Sponge) is not affected.
- Score
- CVSS 4.0 8.7 High
- Status
- Deferred - security-advisories@github.com
- Published
- 2026-03-12
- Last modified
- 2026-03-13
- Weaknesses
- CWE-328
Affected products
References
- https://github.com/stellar/rs-soroban-poseidon/pull/10
- https://github.com/stellar/rs-soroban-poseidon/releases/tag/v25.0.1
- https://github.com/stellar/rs-soroban-poseidon/security/advisories/GHSA-g2p6-hh5v-7hfm
