# imgproxy unbounded memory allocation in ICO loader

Source: https://junglewise.ai/threats/imgproxy-has-unbounded-memory-allocation-in-ico-loader-that-allows-3a1b25fc  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-10-30. Updated: 2026-10-30  
License: CC BY 4.0 with a link back

Severity: high · CVSS 7.5 · Published 2026-10-30

imgproxy is an image processing server that handles image format conversion and optimization. An attacker can send a specially crafted 23-byte ICO (icon) file that triggers a ~4GB memory allocation attempt, causing worker process crashes or sustained memory exhaustion. This requires no authentication and can be exploited repeatedly to exhaust available memory on the host.

Technologies: [github.com/imgproxy/imgproxy/v3 (Go)](https://junglewise.ai/threats/technologies/github-com-imgproxy-imgproxy-v3), [Imgproxy](https://junglewise.ai/threats/technologies/imgproxy). Vendors: [Go](https://junglewise.ai/threats/vendors/go), [Imgproxy](https://junglewise.ai/threats/vendors/imgproxy).

## Quick answers

**Is This vulnerability exploited in the wild?** No. Junglewise Threat Intelligence has no report of This vulnerability being exploited in the wild.

**How severe is This vulnerability?** High severity, with a CVSS score of 7.5, published 30 October 2026.

**Which products and versions are affected?** github.com/imgproxy/imgproxy/v3 (Go) >= 3.3.0, <= 4.0.15, SEMVER:introduced=3.3.0,fixed=4.0.16; Imgproxy v4.0.15 and 3.3.x series.

**Is there a fix for This vulnerability?** Yes. github.com/imgproxy/imgproxy/v3 (Go): upgrade to 4.0.16 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

**How is This vulnerability attacked?** It is attacked over the network, in a hosted service.

**Am I affected?** Check whether you run github.com/imgproxy/imgproxy/v3 (Go) or Imgproxy at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## How to fix

- github.com/imgproxy/imgproxy/v3 (Go): upgrade to 4.0.16 or later

  ```sh
  go get github.com/imgproxy/imgproxy/v3@v4.0.16
  ```


## Technical details

The ICO loader in vips/icoload.c reads an untrusted data_size field (u32) from the ICO directory entry and passes it directly to VIPS_MALLOC without validation. No bounds check occurs on the allocation size, and no verification is performed that the file actually contains the declared amount of data. An attacker sending a crafted ICO file with data_size set to 0xfa000068 (~4GB) causes an immediate ~4GB allocation attempt, leading to out-of-memory conditions or worker crashes.

## Affected products

- imgproxy imgproxy v4.0.15 and 3.3.x series

## Timeline

- 2026-10-30: disclosed

## Related threats

- [imgproxy integer overflow in ICO loader](https://junglewise.ai/threats/cve-2026-123614-imgproxy-from-4-0-0-before-4-0-16-contains-an-integer-overflow)
- [imgproxy unbounded memory allocation in ICO loader](https://junglewise.ai/threats/go-2026-6898-imgproxy-has-unbounded-memory-allocation-in-ico-loader-a99ea6ff)
- [imgproxy out-of-bounds heap read/write in ICO loader BMP header](https://junglewise.ai/threats/go-2026-6895-imgproxy-has-out-of-bounds-heap-read-write-in-ico-loader-d8e85817)
- [imgproxy integer overflow in ICO loader](https://junglewise.ai/threats/go-2026-6897-imgproxy-has-integer-overflow-in-imgproxy-ico-loader-that-dbf52154)
- [imgproxy integer overflow in ICO loader](https://junglewise.ai/threats/imgproxy-has-integer-overflow-in-imgproxy-ico-loader-that-causes-denial-19f131eb)