| # Darknet Integer Overflow in make_convolutional_layer() |
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| ## Vulnerability Summary |
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| Darknet's `make_convolutional_layer()` in `src/convolutional_layer.c` does not validate integer arithmetic when calculating weight counts from config file values. An attacker who provides a malicious `.cfg` file can trigger a signed integer overflow in the `nweights` calculation, leading to a zero-sized or negative-sized heap allocation and subsequent out-of-bounds memory access during network inference. |
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| ## Technical Details |
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| **Location**: `src/convolutional_layer.c`, function `make_convolutional_layer()`, line ~543 |
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| ```c |
| l.nweights = (c / groups) * n * size * size; |
| ``` |
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| All variables are `int` (32-bit signed). No overflow check is performed. |
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| **Trigger**: Config values `channels=46341, filters=46341, size=1, groups=1` |
| - `nweights = 46341 * 46341 * 1 * 1 = 2,147,488,281` |
| - This exceeds `INT_MAX` (2,147,483,647) and wraps to **-2,147,479,015** |
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| **Consequences**: |
| 1. `l.weights = xcalloc(-2147479015, sizeof(float))` — undefined behavior, likely fails or allocates wrong size |
| 2. `l.binary_weights = xcalloc(-2147479015, sizeof(float))` — same issue |
| 3. Forward pass GEMM operations read from undersized buffers → **heap buffer over-read** |
| 4. Potential for information disclosure or code execution depending on memory layout |
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| ## PoC Files |
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| - `poc_overflow.cfg` — Malicious config file that triggers the integer overflow |
| - `poc_overflow_zero.cfg` — Variant that causes nweights to overflow to exactly 0 |
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| ## Reproduction |
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| ```bash |
| git clone https://github.com/AlexeyAB/darknet.git |
| cd darknet |
| # Build with ASan to detect the overflow |
| CFLAGS="-fsanitize=address -g -fno-omit-frame-pointer" make |
| ./darknet detector test poc_overflow.cfg |
| # ASan will report: calloc parameters overflow / heap-buffer-overflow |
| ``` |
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| ## Novelty |
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| - No existing CVEs for Darknet on GitHub Security Advisories or NVD |
| - No existing Huntr submissions for Darknet |
| - No security-related commits on `convolutional_layer.c` since 2021 |
| - The vulnerability is in the config parser's math, not in model file loading |
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| ## Severity |
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| **High** — Integer overflow leading to heap buffer over-read. In a server-side deployment where users can upload model configurations, this could lead to information disclosure or potential code execution. |
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| ## Discovery |
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| Found by Clawd (OWL) for Huntr bug bounty program, May 2026. |
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