A security flaw has been discovered in Nothings stb_image up to 2.30. This affects the function stbi__gif_load_next of the file stb_image.h of the component Multi-frame GIF File Handler. The manipulation results in heap-based buffer overflow. The attack requires a local approach. The exploit has been released to the public and may be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.

stb_image is a single file MIT licensed library for processing images. If `stbi__load_gif_main` in `stbi_load_gif_from_memory` fails it returns a null pointer and may keep the `z` variable uninitialized. In case the caller also sets the flip vertically flag, it continues and calls `stbi__vertical_flip_slices` with the null pointer result value and the uninitialized `z` value. This may result in a program crash.

stb_image is a single file MIT licensed library for processing images. It may look like `stbi__load_gif_main` doesn’t give guarantees about the content of output value `*delays` upon failure. Although it sets `*delays` to zero at the beginning, it doesn’t do it in case the image is not recognized as GIF and a call to `stbi__load_gif_main_outofmem` only frees possibly allocated memory in `*delays` without resetting it to zero. Thus it would be fair to say the caller of `stbi__load_gif_main` is responsible to free the allocated memory in `*delays` only if `stbi__load_gif_main` returns a non null value. However at the same time the function may return null value, but fail to free the memory in `*delays` if internally `stbi__convert_format` is called and fails. Thus the issue may lead to a memory leak if the caller chooses to free `delays` only when `stbi__load_gif_main` didn’t fail or to a double-free if the `delays` is always freed

stb_image is a single file MIT licensed library for processing images. A crafted image file can trigger `stbi__load_gif_main_outofmem` attempt to double-free the out variable. This happens in `stbi__load_gif_main` because when the `layers * stride` value is zero the behavior is implementation defined, but common that realloc frees the old memory and returns null pointer. Since it attempts to double-free the memory a few lines below the first “free”, the issue can be potentially exploited only in a multi-threaded environment. In the worst case this may lead to code execution.

stb_image is a single file MIT licensed library for processing images. The stbi__getn function reads a specified number of bytes from context (typically a file) into the specified buffer. In case the file stream points to the end, it returns zero. There are two places where its return value is not checked: In the `stbi__hdr_load` function and in the `stbi__tga_load` function. The latter of the two is likely more exploitable as an attacker may also control the size of an uninitialized buffer.

stb_image is a single file MIT licensed library for processing images. When `stbi_set_flip_vertically_on_load` is set to `TRUE` and `req_comp` is set to a number that doesn’t match the real number of components per pixel, the library attempts to flip the image vertically. A crafted image file can trigger `memcpy` out-of-bounds read because `bytes_per_pixel` used to calculate `bytes_per_row` doesn’t match the real image array dimensions.

stb_image is a single file MIT licensed library for processing images. A crafted image file may trigger out of bounds memcpy read in `stbi__gif_load_next`. This happens because two_back points to a memory address lower than the start of the buffer out. This issue may be used to leak internal memory allocation information.