CVE-2026-44637 Details
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.
A signed integer overflow vulnerability has been identified in libsixel, a SIXEL encoder/decoder library. This issue arises in versions 0.11.0 through 1.8.7-r1, where the SIXEL parser's image-buffer doubling loop allows for an out-of-bounds heap write in the function sixel_decode_raw_impl. The vulnerability is triggered when context->pos_x, which increases by repeat_count for each SIXEL character without an upper limit check, approaches INT_MAX. This causes the buffer sizing expression 'pos_x + repeat_count' to overflow, bypassing the resize check that prevents oversized buffers. As a result, a large, attacker-influenced offset is computed and written past the allocated memory, leading to potential memory corruption.
Users can upgrade to libsixel version 1.8.7-r2, where this vulnerability has been fixed.
Metrics
CVSS 4.0 Severity and Vector Strings:
No CVSS 4.0 data is available for this CVE.
CVSS 3.x Severity and Vector Strings:
No data available for CVSS Version 2.0 on this CVE.
CISA-ADP
Assessed May 15, 2026References to Advisories, Solutions, and Tools
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| URL | Source(s) | Tag(s) |
|---|---|---|
| https://github.com/saitoha/libsixel/security/advisories/GHSA-9jm7-77gr-qghv | CISA-ADP | ExploitVendor Advisory |
| https://github.com/saitoha/libsixel/security/advisories/GHSA-9jm7-77gr-qghv | [email protected] | ExploitVendor Advisory |
Weakness Enumeration
| CWE-ID | CWE Name | Source |
|---|---|---|
| CWE-787 | Out-of-bounds Write | [email protected] |
| CWE-190 | Integer Overflow or Wraparound | [email protected] |
| CWE-787 | Out-of-bounds Write | [email protected] |
Affected Products
| Product | Versions |
|---|---|
| saitoha libsixel | >= 0.11.0, < 1.8.7-r2 |
CPE
Remediation
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Change History
5 change records found show changes
| Date | Action | Recorded By |
|---|---|---|
| Jun 17, 2026 | CVE Modified | [email protected] |
| Jun 17, 2026 | CVE Modified | CISA-ADP |
| May 15, 2026 | Initial Analysis | [email protected] |
| May 15, 2026 | CVE Modified | CISA-ADP |
| May 14, 2026 | New CVE Received | [email protected] |