ollama-gguf-dos-2

GGUF readString() Integer Overflow — DoS PoC

WARNING: MALICIOUS FILE — SECURITY RESEARCH ONLY

Vulnerability

File: fs/gguf/gguf.go Function: readString() Type: Denial of Service (Integer Overflow → OOM)

Description

readString() reads a uint64 string length from the GGUF file and casts it to int for the bounds check. When the uint64 has the sign bit set (≥ 2^63), the cast produces a negative int, bypassing the bounds check entirely.

func readString(f *File) (string, error) {
    n, err := read[uint64](f)   // n = 0x8000000000000000
    if int(n) > len(f.bts) {    // int(0x8000000000000000) = -9223372036854775808
        f.bts = make([]byte, n)  // make([]byte, 2^63) → OOM panic!
    }
    ...
}

With string_length = 0x8000000000000000 (2^63):

• int(0x8000000000000000) = -9223372036854775808 (negative!)
• make([]byte, 2^63) → Go runtime panic: allocation too large

Impact

• Severity: High (CVSS 7.5)
• Attack Vector: Upload malicious GGUF → Ollama calls readString() → OOM crash
• Authentication: None required
• Affected Versions: Ollama with Go GGUF parser (unpatched)

Reproduction

curl -X POST http://localhost:11434/api/create -d @malicious_gguf_overflow.gguf
# Result: OOM panic → service crash

Fix

if n > 1<<30 {
    return "", errors.New("string length exceeds limit")
}

References

• https://huntr.com/repos/ollama/ollama