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    CVE-2020-21548

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

    Published:Sep 17, 2021
    Last Modified:Apr 24, 2026
    EPS:Sep 17, 2021
    EPSS Score:0.00381
    CVSS Score:8.8

    Affected Products

    Vendor
    Saitoha
    Product
    Libsixel

    Exploits

    https://github.com/saitoha/libsixel/issues/116https://github.com/saitoha/libsixel/issues/116

    Common Weakness Enumeration

    CWE-787 Out-of-bounds Write

    Common Attack Pattern Enumeration and Classification (CAPEC)

    No CAPEC recorded yet

    Related CVEs

    CVE-2026-44637 (CVSS 7.1) — libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, a signed int…
    CVE-2026-44636 (CVSS 7.4) — libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, signed integ…
    CVE-2026-44638 (CVSS 2.5) — libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. From to 1.8.7-r1, a wrong NULL…
    CVE-2026-33023 (CVSS 7.8) — libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. In versions 1.8.7 and prior, wh…
    CVE-2026-33021 (CVSS 7.3) — libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contai…
    CVE-2026-33020 (CVSS 7.1) — libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contai…
    CVE-2026-33019 (CVSS 7.1) — libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contai…
    CVE-2026-33018 (CVSS 7) — libsixel is a SIXEL encoder/decoder implementation derived from kmiya's sixel. Versions 1.8.7 and prior contai…
    CVE-2025-61146 (CVSS 4) — saitoha libsixel until v1.8.7 was discovered to contain a memory leak via the component malloc_stub.c.…
    CVE-2025-9300 (CVSS 1.9) — A vulnerability was found in saitoha libsixel up to 1.10.3. Affected by this issue is the function sixel_debug…

    Common Vulnerability Scoring System

    Attack Vector
    Network
    Adjacent
    Local
    Physical
    Privileges Required
    None
    Low
    High
    User Interaction
    None
    Required
    Scope
    Unchanged
    Changed
    Confidentiality
    None
    Low
    High
    Integrity
    None
    Low
    High
    Availability
    None
    Low
    High