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Fencer Vulns
low 2.5

CVE-2026-44638 json

libsixel: NULL pointer dereference

published 2026-05-14 5 mo ago modified 2026-10-26 13 d ago also EUVD-2026-30411

cvss
2.5
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.1%
EPSS 0.1% chance of exploitation in 30 days, percentile 2%
public exploits
0
none known

Summary

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.

Patch / fix

  • libsixel_project libsixel 1.8.7-r2
  • saitoha libsixel 1.8.7-r2
  • libsixel Debian 14 1:1.8.7-r2-1

debian advisories DEBIAN-CVE-2026-44638

  • libsixel openSUSE Tumbleweed 1.10.5-3.1

opensuse advisories openSUSE-SU-2026:12420-1

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2026-44638 updated cvss 2.5

libsixel: libsixel: Denial of Service due to NULL pointer dereference during memory allocation

  • Red Hat All currently supported Red Hat products
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
5 mo ago

Exploit prediction

0.13% chance of exploitation in the next 30 days, higher than 2% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 3.1 2.5 CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L
NVD 3.1 2.5 CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L

Affected products

  • saitoha libsixel

Classification

Weakness
  • CWE-476 NULL Pointer Dereference
  • CWE-690 Unchecked Return Value to NULL Pointer Dereference

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

CPEs and fixed versions use Anchore's correction of NVD's data: Added CPE configurations because not yet analyzed by NVD.