CVE-2026-32129: soroban-poseidon provides Poseidon and Poseidon2 cryptographic hash functions for Soroban smart contracts. Poseidon V1 (PoseidonSponge) accepts variab...

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.

Metrics

CVSS 4.0

8.7/10

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/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X

EPSS Probability

0.22%

12.5th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-328

References

Timeline

Published: Mar 12, 2026
Last Modified: Jun 17, 2026
Status: Deferred

Frequently Asked Questions

What is 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.

How severe is CVE-2026-32129?

CVE-2026-32129 has a CVSS score of 8.7/10 (HIGH severity). The EPSS model estimates a 0.22% probability of exploitation in the next 30 days.

How do I fix CVE-2026-32129?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.