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Vulnerability record · CVE-2020-21548 · published 17 September 2021

CVE-2020-21548: Saitoha libsixel out-of-bounds write vulnerability

SSaitoha · Libsixel

Libsixel 1.8.3 contains a heap-based buffer overflow in the sixel_encode_highcolor function in tosixel.c.

8.8 CVSS 3.1 High EPSS 1.1% · top 36.6% CWE-787 · Out-of-bounds write
8.8CVSS 3.1 base score, v2 6.8
1.1%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
2References, 2 tagged exploit
17 Jun 2026Last modified by NVD

Description

Libsixel 1.8.3 contains a heap-based buffer overflow in the sixel_encode_highcolor function in tosixel.c.

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

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
https://github.com/saitoha/libsixel/issues/116 ExploitIssue TrackingPatchThird Party Advisory
https://github.com/saitoha/libsixel/issues/116 ExploitIssue TrackingPatchThird Party Advisory

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Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2019-19637Saitoha libsixel integer overflow vulnerabilityAn issue was discovered in libsixel 1.8.2. There is an integer overflow in the function sixel_decode_raw_impl at fromsixel.c.EPSS 1.2%9.8CVE-2019-19638Saitoha libsixel integer overflow vulnerabilityAn issue was discovered in libsixel 1.8.2. There is a heap-based buffer overflow in the function load_pnm at frompnm.c, due to an integer overflow.EPSS 1.2%9.8CVE-2019-19635Saitoha libsixel out-of-bounds write vulnerabilityAn issue was discovered in libsixel 1.8.2. There is a heap-based buffer overflow in the function sixel_decode_raw_impl at fromsixel.c.EPSS 1.2%9.8CVE-2019-19636Saitoha libsixel integer overflow vulnerabilityAn issue was discovered in libsixel 1.8.2. There is an integer overflow in the function sixel_encode_body at tosixel.c.EPSS 1.2%8.8CVE-2022-27044Saitoha libsixel out-of-bounds write vulnerabilitylibsixel 1.8.6 is affected by Buffer Overflow in libsixel/src/quant.c:876.EPSS 1.0%8.8CVE-2022-27046Saitoha libsixel use after free vulnerabilitylibsixel 1.8.6 suffers from a Heap Use After Free vulnerability in in libsixel/src/dither.c:388.EPSS 1.0%8.8CVE-2020-21547Saitoha libsixel out-of-bounds write vulnerabilityLibsixel 1.8.2 contains a heap-based buffer overflow in the dither_func_fs function in tosixel.c.EPSS 1.1%8.8CVE-2019-20205Saitoha libsixel integer overflow vulnerabilitylibsixel 1.8.4 has an integer overflow in sixel_frame_resize in frame.c.EPSS 1.0%

Source: NIST National Vulnerability Database (record CVE-2020-21548), CISA KEV, FIRST EPSS (scores of 2026-09-27). This page is refreshed as NVD updates the record.