CVE-2026-44638 Details
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.
A NULL pointer dereference vulnerability has been identified in libsixel versions 1.0.0 through 1.8.7-r1. The issue arises in the functions sixel_decode_raw and the deprecated sixel_decode, where a faulty NULL check after a memory allocation call allows for a NULL pointer dereference when the allocation fails. Instead of checking the value returned by malloc, the check incorrectly verifies the address of the output parameter, which is always non-NULL. As a result, when memory allocation fails, the function continues executing and writes through a NULL pointer, leading to a process crash. This vulnerability causes a denial-of-service condition for any caller of these public APIs that experiences low memory.
Users can upgrade to libsixel version 1.8.7-r2, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 15, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w | CISA-ADP | ExploitVendor Advisory |
| https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w | [email protected] | ExploitVendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-476 | NULL Pointer Dereference | [email protected] |
| CWE-476 | NULL Pointer Dereference | [email protected] |
| CWE-690 | Unchecked Return Value to NULL Pointer Dereference | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| saitoha libsixel | >= 1.0.0, < 1.8.7-r2 |
CPE
Remediation
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Change History
5 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 15, 2026 | Initial Analysis | [email protected] |
| May 15, 2026 | CVE Modified | CISA-ADP |
| May 14, 2026 | New CVE Received | [email protected] |