CVE-2026-44638 libsixel: NULL pointer dereference
A NULL pointer dereference in libsixel causes a crash when memory allocation fails, leading to denial of service for applications using the library.
- 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
What is CVE-2026-44638?
CVE-2026-44638 is a low-severity vulnerability in saitoha libsixel, published on 14 May 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. From to 1.8.7-r1, a wrong NULL check after an allocation call in sixel_decode_raw and sixel_decode causes a NULL pointer dereference whenever the allocation fails. The check tests the address of the output parameter (always non-NULL) instead of the value the malloc returned. On allocation failure, the function continues and writes through a NULL pointer, crashing the process. This is a denial of service against any caller of these public APIs that hits a low-memory condition. This vulnerability is fixed in 1.8.7-r2.
Which versions are affected by CVE-2026-44638?
It affects 1 product.
Products include Saitoha Libsixel.
How do I fix CVE-2026-44638?
Upgrade to a fixed version.
Is CVE-2026-44638 being exploited?
It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-44638 exists.
Other vulnerabilities in saitoha libsixel
Sources
Also known as DEBIAN-CVE-2026-44638, GHSA-wpx3-h5g8-qr3w, UBUNTU-CVE-2026-44638.