CVE-2026-44638

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.

CVSS v3.1 Score

2.5

LOW

CVSS:3.1/AV:L/AC:H/PR:N/UI:R/S:U/C:N/I:N/A:L

EPSS — Exploit Prediction

0.0002

Probability of exploitation

0.05%

Percentile rank

EPSS estimates the probability that this vulnerability will be exploited in the wild within the next 30 days. A higher score means more likely to be exploited.

Weakness Type (CWE)

CWE-476 CWE-476

CWE-690 CWE-690

Affected Products

Vendor	Product	Versions
saitoha	libsixel	1.0.0 — 1.8.7-r2

References

Advisories & Patches

https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w

Exploits

https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w https://github.com/saitoha/libsixel/security/advisories/GHSA-wpx3-h5g8-qr3w

Frequently Asked Questions

What is CVE-2026-44638? +

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. It has a CVSS v3.1 base score of 2.5 (LOW).

How severe is CVE-2026-44638? +

CVE-2026-44638 has a CVSS v3.1 score of 2.5 out of 10, rated LOW. This is a low-severity vulnerability with limited impact. The EPSS score is 0.0002, placing it in the 0th percentile for exploitation probability.

What products are affected by CVE-2026-44638? +

CVE-2026-44638 affects products from saitoha, specifically: libsixel. Check the affected products table above for specific version ranges.

How do I check if I'm vulnerable to CVE-2026-44638? +

You can use Secably's free Website Scanner to check your website for known vulnerabilities. For infrastructure scanning, use the Port Scanner to identify exposed services that may be affected. Check the vendor advisories linked above for specific patch and version information.

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