saitoha libsixel up to 1.8.7-r1 SIXEL Encoder sixel_decode_raw_impl integer overflow

Summaryinfo

A vulnerability marked as problematic has been reported in saitoha libsixel up to 1.8.7-r1. The impacted element is the function sixel_decode_raw_impl of the component SIXEL Encoder. This manipulation causes integer overflow. This vulnerability is tracked as CVE-2026-44637. The attack is possible to be carried out remotely. No exploit exists. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability classified as problematic was found in saitoha libsixel up to 1.8.7-r1. Affected by this vulnerability is the function sixel_decode_raw_impl of the component SIXEL Encoder. The manipulation with an unknown input leads to a integer overflow vulnerability. The CWE definition for the vulnerability is CWE-190. The product performs a calculation that can produce an integer overflow or wraparound, when the logic assumes that the resulting value will always be larger than the original value. This can introduce other weaknesses when the calculation is used for resource management or execution control. As an impact it is known to affect integrity, and availability. The summary by CVE is:

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.

The advisory is shared at github.com. This vulnerability is known as CVE-2026-44637 since 05/07/2026. The exploitation appears to be easy. The attack can be launched remotely. The exploitation doesn't need any form of authentication. It demands that the victim is doing some kind of user interaction. Technical details are known, but no exploit is available.

The vulnerability scanner Nessus provides a plugin with the ID 314941 (Linux Distros Unpatched Vulnerability : CVE-2026-44637), which helps to determine the existence of the flaw in a target environment.

Upgrading to version 1.8.7-r2 eliminates this vulnerability.

The vulnerability is also documented in the vulnerability database at Tenable (314941). If you want to get the best quality for vulnerability data then you always have to consider VulDB.

Productinfo

Vendor

• saitoha

Name

• libsixel

Version

• 1.8.7-r1

License

• open-source

Website

• Product: https://github.com/saitoha/libsixel/

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If you want to get the best quality for vulnerability data then you always have to consider VulDB.

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