# CVE-2026-33019: libsixel: Integer overflow leads to Out-of-bounds Read in img2sixel

> An integer overflow in libsixel's img2sixel tool allows attackers to trigger out-of-bounds heap reads via crafted crop arguments, causing crashes or information disclosure.

- **Severity:** High 7.1 (`CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Local or same network only
- **Victim action needed:** A user has to click or open something
- **Fix available:** Yes
- **Published:** 14 Apr 2026
- **Updated:** 15 Apr 2026
- **Also known as:** DEBIAN-CVE-2026-33019, GHSA-c854-ffg9-g72c, UBUNTU-CVE-2026-33019

## What is CVE-2026-33019?

CVE-2026-33019 is a high-severity vulnerability in saitoha libsixel, published on 14 Apr 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.

### Official description

libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contain an integer overflow leading to an out-of-bounds heap read in the --crop option handling of img2sixel, where positive coordinates up to INT_MAX are accepted without overflow-safe bounds checking. In sixel_encoder_do_clip(), the expression clip_w + clip_x overflows to a large negative value when clip_x is INT_MAX, causing the bounds guard to be skipped entirely, and the unclamped coordinate is passed through sixel_frame_clip() to clip(), which computes a source pointer far beyond the image buffer and passes it to memmove(). An attacker supplying a specially crafted crop argument with any valid image can trigger an out-of-bounds read in the heap, resulting in a reliable crash and potential information disclosure. This issue has been fixed in version 1.8.7-r1.

Weakness: CWE-190 (Integer Overflow or Wraparound), CWE-125 (Out-of-bounds Read)

## Which versions are affected by CVE-2026-33019?

It affects 1 product.


Products: Saitoha Libsixel.

## How do I fix CVE-2026-33019?

Upgrade to a fixed version.

## Is CVE-2026-33019 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33019 exists.

## Other vulnerabilities in saitoha libsixel

- [CVE-2019-19635](https://insights.sbomify.com/CVE-2019-19635/): Memory corruption in n/a (critical 9.8)
- [CVE-2019-19636](https://insights.sbomify.com/CVE-2019-19636/): Integer overflow in n/a (critical 9.8)
- [CVE-2019-19637](https://insights.sbomify.com/CVE-2019-19637/): Integer overflow in n/a (critical 9.8)
- [CVE-2019-19638](https://insights.sbomify.com/CVE-2019-19638/): Integer overflow in n/a (critical 9.8)
- [CVE-2022-27044](https://insights.sbomify.com/CVE-2022-27044/): Memory corruption in n/a (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-33019 and fix it if it is affected.

What it is: CVE-2026-33019 is a high-severity vulnerability in saitoha libsixel, published on 14 Apr 2026. It can only be exploited from the same machine or local network, and only if a user opens a file or follows a link.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-33019 exists.

Affected product: saitoha libsixel. No package-level version data is available, so check the vendor advisory linked from the reference page.

Task:
1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies.
2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it.
3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead.
4. Run the tests and summarise what changed and why.
5. If nothing in the project is affected, say so and change nothing.

Reference: https://insights.sbomify.com/CVE-2026-33019/ (Markdown: https://insights.sbomify.com/CVE-2026-33019/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-33019
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-33019
- OSV: https://osv.dev/vulnerability/CVE-2026-33019

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-33019/
Summaries are generated and may contain mistakes; the official description above is the record.