The fix to https://cantina.xyz/code/c486d600-bed0-4fc6-aed1-de759fd29fa2/findings/21 has a typo that still results in the highest limb of pc being range checked to 8-bits instead of 6-bits.
In the AIR, we do https://github.com/openvm-org/openvm/blob/0f94c8a3dfa7536c1231465d1bdee5fc607a5993/extensions/rv32im/circuit/src/auipc/core.rs#L135
        for (i, limb) in pc_limbs.iter().skip(1).enumerate() {
            if i == pc_limbs.len() - 1 {
It should be
        for (i, limb) in pc_limbs.iter().enumerate().skip(1) {
Right now the if statement is never triggered because the enumeration gives i=0,1,2 when we instead want i=1,2,3. What this means is that pc_limbs[3] is range checked to 8-bits instead of 6-bits.
This leads to a vulnerability where the pc_limbs decomposition differs from the true pc, which means a malicious prover can make the destination register take a different value than the AUIPC instruction dictates, by making the decomposition overflow the BabyBear field.
{
    "nvd_published_at": "2025-05-02T23:15:16Z",
    "github_reviewed_at": "2025-05-05T19:57:09Z",
    "cwe_ids": [
        "CWE-131"
    ],
    "severity": "HIGH",
    "github_reviewed": true
}