CVE-2020-21677
A heap-based buffer overflow in the sixel_encoder_output_without_macro function in encoder.c of...
CVE-2020-21677 is a medium vulnerability (CVSS 6.5) in Saitoha Libsixel, published August 10, 2021. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.90%, the 59th percentile. Fixed in libsixel 1.8.6-1.
A heap-based buffer overflow in the sixel_encoder_output_without_macro function in encoder.c of Libsixel 1.8.4 allows attackers to cause a denial of service (DOS) via converting a crafted PNG file into Sixel format.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- High
Exploit likelihood
What each source reports
NVD Score used
A heap-based buffer overflow in the sixel_encoder_output_without_macro function in encoder.c of Libsixel 1.8.4 allows attackers to cause a denial of service (DOS) via converting a crafted PNG file into Sixel format.
- Record
CVE-2020-21677- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - CVSS 2.0
- 4.3 Medium
AV:N/AC:M/Au:N/C:N/I:N/A:P - Weakness
- CWE-787
- Updated
- 2026-11-02
CVE List No score
A heap-based buffer overflow in the sixel_encoder_output_without_macro function in encoder.c of Libsixel 1.8.4 allows attackers to cause a denial of service (DOS) via converting a crafted PNG file into Sixel format.
- Record
CVE-2020-21677- Updated
- 2026-11-02
EUVDEUVD-2020-14445 No score
A heap-based buffer overflow in the sixel_encoder_output_without_macro function in encoder.c of Libsixel 1.8.4 allows attackers to cause a denial of service (DOS) via converting a crafted PNG file into Sixel format.
- Record
EUVD-2020-14445- Updated
- 2026-11-03
GitHub AdvisoriesGHSA-j9fq-4p85-2pqh
A heap-based buffer overflow in the sixel_encoder_output_without_macro function in encoder.c of...
A heap-based buffer overflow in the sixel_encoder_output_without_macro function in encoder.c of Libsixel 1.8.4 allows attackers to cause a denial of service (DOS) via converting a crafted PNG file into Sixel format.
- Record
GHSA-j9fq-4p85-2pqh- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Weakness
- CWE-787
- Updated
- 2026-11-02
OSV
A heap-based buffer overflow in the sixel_encoder_output_without_macro function in encoder.c of Libsixel 1.8.4 allows attackers to cause a denial of service (DOS) via converting a crafted PNG file into Sixel format.
- Record
CVE-2020-21677- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVDEBIAN-CVE-2020-21677
A heap-based buffer overflow in the sixel_encoder_output_without_macro function in encoder.c of Libsixel 1.8.4 allows attackers to cause a denial of service (DOS) via converting a crafted PNG file into Sixel format.
- Record
DEBIAN-CVE-2020-21677- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
OSVUBUNTU-CVE-2020-21677
A heap-based buffer overflow in the sixel_encoder_output_without_macro function in encoder.c of Libsixel 1.8.4 allows attackers to cause a denial of service (DOS) via converting a crafted PNG file into Sixel format.
- Record
UBUNTU-CVE-2020-21677- CVSS 3.1
- 6.5 Medium
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H - Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
libsixelDebian:12 |
before 1.8.6-1 | 1.8.6-1 |
libsixelDebian:13 |
before 1.8.6-1 | 1.8.6-1 |
libsixelDebian:14 |
before 1.8.6-1 | 1.8.6-1 |
libsixelUbuntu:16.04:LTS |
All versions, plus listed versions 1.4.2-11.5.2-2 |
None known |
libsixelUbuntu:18.04:LTS |
All versions, plus listed versions 1.5.2-21.7.3-1 |
None known |
libsixelUbuntu:20.04:LTS |
All versions, plus listed versions 1.8.2-11.8.2-2.1 |
None known |
libsixelUbuntu:22.04:LTS |
All versions, plus listed versions 1.8.6-21.10.3-21.10.3-3 |
None known |
libsixelUbuntu:24.04:LTS |
All versions, plus listed versions 1.10.3-31.10.3-3build1 |
None known |
libsixelUbuntu:25.10 |
All versions, plus listed versions 1.10.5-1 |
None known |
libsixelUbuntu:26.10 |
All versions, plus listed versions 1.10.5-1build11:1.8.7-r2-1 |
None known |
libsixelUbuntu:26.04:LTS |
All versions, plus listed versions 1.10.5-11.10.5-1build1 |
None known |
History
| When | Changed | Sources |
|---|---|---|
| 2026-11-03 | aliases | EUVD |
| 2026-11-02 | created | CVE List, GitHub Advisories, NVD, OSV |