CVE-2026-33018: CWE-416: Use After Free in saitoha libsixel
libsixel versions prior to 1. 8. 7-rc1 contain a Use-After-Free vulnerability in the load_gif() function when processing animated GIFs. The vulnerability arises because a sixel_frame_t object is reused across frames, and its pixel buffer is freed and reallocated without checking reference counts, leading to dangling pointers. Applications using sixel_helper_load_image_file() with multi-frame callbacks can experience crashes or potentially code execution. This issue is fixed in version 1. 8. 7-r1.
AI Analysis
Technical Summary
The vulnerability in libsixel (CVE-2026-33018) is a Use-After-Free (CWE-416) in the load_gif() function of fromgif.c. It occurs because the sixel_frame_t object is reused for all frames of an animated GIF, and gif_init_frame() frees and reallocates the pixel buffer without verifying the reference count. The public API allows retaining frames and accessing raw pixel buffers, but after the second frame is decoded, callbacks holding these pointers encounter dangling references, confirmed by ASAN. This leads to a reliable crash and potential code execution in applications using sixel_helper_load_image_file() with multi-frame callbacks on user-supplied animated GIFs. The vulnerability affects versions prior to 1.8.7-rc1 and has been fixed in version 1.8.7-r1.
Potential Impact
Exploitation of this vulnerability can cause reliable application crashes and may allow remote code execution when processing malicious animated GIFs. The impact includes confidentiality, integrity, and availability compromise as indicated by the CVSS vector (C/C/I/A: High). The vulnerability requires local access (AV:L) with high attack complexity and user interaction.
Mitigation Recommendations
Upgrade to libsixel version 1.8.7-r1 or later, where this Use-After-Free vulnerability has been fixed. No other mitigation or temporary workaround is documented. Patch status is confirmed by the vendor fix in version 1.8.7-r1.
CVE-2026-33018: CWE-416: Use After Free in saitoha libsixel
Description
libsixel versions prior to 1. 8. 7-rc1 contain a Use-After-Free vulnerability in the load_gif() function when processing animated GIFs. The vulnerability arises because a sixel_frame_t object is reused across frames, and its pixel buffer is freed and reallocated without checking reference counts, leading to dangling pointers. Applications using sixel_helper_load_image_file() with multi-frame callbacks can experience crashes or potentially code execution. This issue is fixed in version 1. 8. 7-r1.
AI-Powered Analysis
Machine-generated threat intelligence
Technical Analysis
The vulnerability in libsixel (CVE-2026-33018) is a Use-After-Free (CWE-416) in the load_gif() function of fromgif.c. It occurs because the sixel_frame_t object is reused for all frames of an animated GIF, and gif_init_frame() frees and reallocates the pixel buffer without verifying the reference count. The public API allows retaining frames and accessing raw pixel buffers, but after the second frame is decoded, callbacks holding these pointers encounter dangling references, confirmed by ASAN. This leads to a reliable crash and potential code execution in applications using sixel_helper_load_image_file() with multi-frame callbacks on user-supplied animated GIFs. The vulnerability affects versions prior to 1.8.7-rc1 and has been fixed in version 1.8.7-r1.
Potential Impact
Exploitation of this vulnerability can cause reliable application crashes and may allow remote code execution when processing malicious animated GIFs. The impact includes confidentiality, integrity, and availability compromise as indicated by the CVSS vector (C/C/I/A: High). The vulnerability requires local access (AV:L) with high attack complexity and user interaction.
Mitigation Recommendations
Upgrade to libsixel version 1.8.7-r1 or later, where this Use-After-Free vulnerability has been fixed. No other mitigation or temporary workaround is documented. Patch status is confirmed by the vendor fix in version 1.8.7-r1.
Technical Details
- Data Version
- 5.2
- Assigner Short Name
- GitHub_M
- Date Reserved
- 2026-03-17T17:22:14.666Z
- Cvss Version
- 3.1
- State
- PUBLISHED
- Remediation Level
- null
Threat ID: 69deb96d82d89c981f0b1a09
Added to database: 4/14/2026, 10:02:21 PM
Last enriched: 4/14/2026, 10:17:57 PM
Last updated: 4/14/2026, 11:04:19 PM
Views: 4
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