CVE-2026-44638: libsixel: NULL pointer dereference

Severity: low (CVSS 2.5 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.1% probability of exploitation in the next 30 days
Public exploit or detection template: yes
Published: 2026-05-14 · updated 2026-10-26
Weakness: CWE-476

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.

Affected products

saitoha libsixel: from 1.0.0 before 1.8.7-r2 — fixed in 1.8.7-r2

How to fix

Upgrade to a fixed version: saitoha libsixel 1.8.7-r2. Check the vendor advisory for mitigations.

References

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