7.5

CVSS Score

3.1

-

CVSS Score

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GHSA-fj2x-735w-74vq

GHSA-fj2x-735w-74vq: gnark-crypto allows unchecked memory allocation during vector deserialization

The issue has been reported by @raefko from @fuzzinglabs. Excerpts from the report:

A critical vulnerability exists in the gnark-crypto library's Vector.ReadFrom() function that allows an attacker to trigger arbitrary memory allocation by crafting malicious input data. An attacker can cause the verifier to attempt allocating up to 128 GB of memory with a minimal malicious input, leading to out-of-memory crashes and denial of service.

Root Cause

The vulnerability stems from unchecked deserialization of attacker-controlled length fields in the gnark-crypto library's Vector.ReadFrom() function. The function reads a 4-byte unsigned integer from untrusted input and directly uses it to allocate memory without any validation or bounds checking.

Vulnerable Code Path
User Input (Malicious Proof/Data)
         ↓
gnark Proof/Data Deserialization
         ↓
Vector.ReadFrom() (ecc/bn254/fr/vector.go:136-144)
  → sliceLen := binary.BigEndian.Uint32(buf[:4])   // ← ATTACKER-CONTROLLED
  → (*vector) = make(Vector, sliceLen)             // ← UNCHECKED ALLOCATION
         ↓
runtime.makeslice attempts 100+ GB allocation
         ↓
fatal error: runtime: out of memory → SIGABRT
Vulnerable Code

File: gnark-crypto@v0.14.0+/ecc/bn254/fr/vector.go:136-144

The code reads a 4-byte big-endian unsigned integer (sliceLen) directly from the input stream and uses it to allocate a slice without any bounds checking or validation. Each element is 32 bytes (fr.Element for BN254 curve), so an attacker can request up to:

Maximum Allocation: 2^32 elements × 32 bytes = 137,438,953,472 bytes ≈ 128 GB

Root Cause Analysis

The gnark-crypto library implements a generic serialization format for field element vectors. The format is:

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GHSA-fj2x-735w-74vq

GHSA-fj2x-735w-74vq:

7.5

CVSS Score

3.1

-

CVSS Score

Basic Information

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Technical Details

Package Name	Ecosystem	Vulnerable Versions	First Patched Version
github.com/consensys/gnark-crypto	go	>= 0.9.1, < 0.18.1	0.18.1
github.com/consensys/gnark-crypto	go	= 0.19.0	0.19.2

Technical Details

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Root Cause Analysis

The vulnerability lies in the ReadFrom and AsyncReadFrom methods of the Vector type, which are used for deserializing vector data. These methods read a 4-byte length field from the input stream and use it directly to allocate a slice for the vector elements without any bounds checking. An attacker can craft a malicious input with a large length value, causing the program to attempt to allocate a huge amount of memory (up to 128GB), which leads to an out-of-memory error and a denial of service. The patch addresses this by adding a check to limit the maximum allocation size, mitigating the vulnerability. The issue is present in multiple files across the codebase, as this vector implementation is used for various cryptographic curves and fields.

Vulnerable functions

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WAF Rule

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Reasoning

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