jdx/mise · error · eyre::Report

unsupported ELF class

Error message

unsupported ELF class

What it means

Thrown by elf_interpreter when the ELF EI_CLASS byte (byte 4) is neither 1 (ELF32) nor 2 (ELF64). The parser only understands 32- and 64-bit ELF program headers; any other class value means the header is corrupt or the file is not a conventional Linux executable, and parsing cannot continue safely.

Source

Thrown at src/system/remote.rs:1381

        Some(2) => false,
        _ => bail!("unsupported ELF byte order"),
    };
    let (program_offset, entry_size, entry_count, offset_field, size_field) = match class {
        1 => (
            read_elf_int(bytes, 28, 4, little_endian)?,
            read_elf_int(bytes, 42, 2, little_endian)?,
            read_elf_int(bytes, 44, 2, little_endian)?,
            4,
            16,
        ),
        2 => (
            read_elf_int(bytes, 32, 8, little_endian)?,
            read_elf_int(bytes, 54, 2, little_endian)?,
            read_elf_int(bytes, 56, 2, little_endian)?,
            8,
            32,
        ),
        _ => bail!("unsupported ELF class"),
    };
    let program_offset = usize::try_from(program_offset)?;
    let entry_size = usize::try_from(entry_size)?;
    let entry_count = usize::try_from(entry_count)?;
    for index in 0..entry_count {
        let start = program_offset
            .checked_add(
                index
                    .checked_mul(entry_size)
                    .ok_or_else(|| eyre!("invalid ELF program headers"))?,
            )
            .ok_or_else(|| eyre!("invalid ELF program headers"))?;
        if read_elf_int(bytes, start, 4, little_endian)? != PT_INTERP {
            continue;
        }
        let offset = usize::try_from(read_elf_int(
            bytes,
            start + offset_field,

View on GitHub (pinned to 6f52dcdf99)

Solutions

1. Re-obtain the binary from a trusted source and validate the header (readelf -h mise should show Class: ELF64)
2. Strip anything prepended to the file or re-extract the archive properly
3. Use remote_mise/bootstrap_command to sidestep local-binary validation

Example fix

# before: binary with damaged header
readelf -h ./mise  # Class: <invalid>

# after: reinstall
./install-mise.sh   # or: cargo build --release
readelf -h ./target/release/mise  # Class: ELF64

// Same magic/class guard as 895 covers this arm
fn elf_header_sane(path: &Path) -> bool {
    let mut magic = [0u8; 6];
    let Ok(mut f) = std::fs::File::open(path) else { return false };
    std::io::Read::read_exact(&mut f, &mut magic).is_ok()
        && &magic[..4] == b"\x7fELF"
        && matches!(magic[4], 1 | 2)   // ELF32/ELF64 only
        && matches!(magic[5], 1 | 2)
}

fn elf_header_sane(path: &Path) -> bool {
    let mut magic = [0u8; 6];
    let Ok(mut f) = std::fs::File::open(path) else { return false };
    std::io::Read::read_exact(&mut f, &mut magic).is_ok()
        && &magic[..4] == b"\x7fELF"
        && matches!(magic[4], 1 | 2)
        && matches!(magic[5], 1 | 2)
}

match elf_interpreter(&bytes) {
    Err(e) if e.to_string().contains("unsupported ELF class") => {
        eyre::bail!("mise binary at {} is not a valid ELF32/ELF64 image; rebuild it", path.display());
    }
    other => other?,
}

When it happens

Trigger: A truncated or corrupted mise_bin whose class byte is garbage; a crafted/fuzzed binary fed into Linux-to-Linux upload validation.

Common situations: Damaged artifacts from partial copies; test/fuzz corpora accidentally pointed at by mise_bin; files with prepended data (some packers) that shift the header.

Related errors

• unsupported ELF byte order
• local mise is not an ELF executable
• trimPrefix requires exactly 2 arguments
• trimSuffix requires exactly 2 arguments
• action prediction payload is too large

AI-assisted analysis of jdx/mise@6f52dcdf99 (2026-08-22). Data as JSON: /api/errors/e8758a9bddf2af13. Report an issue: GitHub.