CVE-2026-44637: Saitoha Libsixel buffer overflow (CVSS 7.1)

Description

libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, a signed integer overflow in the SIXEL parser's image-buffer doubling loop can lead to an out-of-bounds heap write in sixel_decode_raw_impl. context->pos_x grows by repeat_count on every sixel character with no upper bound check. Once pos_x approaches INT_MAX, the expression "pos_x + repeat_count" used to size the image buffer overflows signed int. Depending on how the overflow wraps, the resize check that should reject oversized buffers can be bypassed, after which a subsequent write computes a large attacker-influenced offset into image->data and writes past the allocation. Reachable from any caller that decodes attacker-supplied SIXEL data, including img2sixel. This vulnerability is fixed in 1.8.7-r2.

CVSS 3.1 breakdown

Attack vectorLocal

Attack complexityLow

Privileges requiredNone

User interactionRequired

ScopeUnchanged

ConfidentialityNone

IntegrityHigh

AvailabilityHigh

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

Affected products

Saitoha Libsixel≥ 0.11.0 < 1.8.7-r2

Remediation

Fixed in

Saitoha Libsixel≥ 1.8.7-r2

Patch & vendor advisories

https://github.com/saitoha/libsixel/security/advisories/GHSA-9jm7-77gr-qghv

References

https://github.com/saitoha/libsixel/security/advisories/GHSA-9jm7-77gr-qghvExploitVendor Advisory

Related CVEs

Recent high-severity vulnerabilities sharing a weakness type.

Frequently asked

Is CVE-2026-44637 being actively exploited?

CVE-2026-44637 is not in the CISA KEV catalog. A public exploit reference exists, so treat it as exploitable. Its EPSS exploit probability is 0.17%.

How severe is CVE-2026-44637?

CVE-2026-44637 has a CVSS 3.1 base score of 7.1, rated high. EPSS estimates a 0.17% probability of exploitation.

Which products are affected by CVE-2026-44637?

Affected products include Saitoha Libsixel.

How do I fix CVE-2026-44637?

Upgrade affected software to a fixed version, for example Saitoha Libsixel 1.8.7-r2 or later, then confirm no affected versions remain in your inventory.

How Secuno handles this

Secuno correlates vulnerabilities like CVE-2026-44637 against the real software inventory on every managed device, as each hourly inventory arrives. Rather than a static severity, each match is scored in context: exploit availability, EPSS, the asset's exposure, and business criticality decide where it lands in the queue. If an affected version is present anywhere across your portfolio, it surfaces automatically with a prioritised remediation path.

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