Bug 2477620 (CVE-2026-44638)

Summary: CVE-2026-44638 libsixel: libsixel: Denial of Service due to NULL pointer dereference during memory allocation
Product: [Other] Security Response Reporter: OSIDB Bzimport <bzimport>
Component: vulnerabilityAssignee: Product Security DevOps Team <prodsec-dev>
Status: NEW --- QA Contact:
Severity: low Docs Contact:
Priority: low    
Version: unspecifiedKeywords: Security
Target Milestone: ---   
Target Release: ---   
Hardware: All   
OS: Linux   
Whiteboard:
Fixed In Version: Doc Type: ---
Doc Text:
A flaw was found in libsixel, a SIXEL encoder/decoder implementation. An incorrect NULL check after a memory allocation call in the `sixel_decode_raw` and `sixel_decode` functions can lead to a NULL pointer dereference. This occurs when memory allocation fails, causing the process to crash and resulting in a Denial of Service (DoS) for any caller of these application programming interfaces (APIs) under low-memory conditions.
 Story Points: ---
Clone Of: Environment:
Last Closed: Type: ---
Regression: --- Mount Type: ---
Documentation: --- CRM:
Verified Versions: Category: ---
oVirt Team: --- RHEL 7.3 requirements from Atomic Host:
Cloudforms Team: --- Target Upstream Version:
Embargoed:

Description OSIDB Bzimport 2026-05-14 21:01:39 UTC 
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.