Vulnerability · Published Mar 12, 2026 · Assigned by GitHub_M
CVE-2026-32129Poseidon V1 variable-length input collision via implicit zero-padding
High 8.7
In plain English
A high-severity security flaw in rs-soroban-poseidon from stellar. There are no confirmed reports of exploitation so far. The chance it is exploited in the next 30 days is estimated at 0.2% (higher than 12% of all known vulnerabilities).
Official description
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.
Affected products (as reported)
| Vendor | Product | Versions |
|---|---|---|
| stellar | rs-soroban-poseidon | < 25.0.1 |
Weakness: CWE-328 · Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N
References
- https://github.com/stellar/rs-soroban-poseidon/security/advisories/GHSA-g2p6-hh5v-7hfm x_refsource_CONFIRM
- https://github.com/stellar/rs-soroban-poseidon/pull/10 x_refsource_MISC
- https://github.com/stellar/rs-soroban-poseidon/releases/tag/v25.0.1 x_refsource_MISC