CVE-2026-44637
libsixel: integer overflow in parser
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.
Attack profile
How easy it is to exploit
- Attack vector
- Local
- Complexity
- Low
- Privileges needed
- None
- User interaction
- Required
What an attacker can affect
- Confidentiality
- None
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
7.1
libsixel: integer overflow in parser
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.
- Record
CVE-2026-44637- CVSS 3.1
- 7.1 High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H - Weakness
- CWE-190, CWE-787
- Updated
- 2026-11-02
EUVDEUVD-2026-30412
7.1
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.
- Record
EUVD-2026-30412- CVSS 3.1
- 7.1 High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H - Updated
- 2026-11-02
NVD
7.1
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.
- Record
CVE-2026-44637- CVSS 3.1
- 7.1 High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H - Weakness
- CWE-190, CWE-787
- Updated
- 2026-11-02
OSV
7.1
libsixel: integer overflow in parser
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.
- Record
CVE-2026-44637- CVSS 3.1
- 7.1 High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H - Weakness
- CWE-190, CWE-787
- Updated
- 2026-11-05
OSVDEBIAN-CVE-2026-44637
7.1
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.
- Record
DEBIAN-CVE-2026-44637- CVSS 3.1
- 7.1 High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-44637
7.1
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.
- Record
UBUNTU-CVE-2026-44637- CVSS 3.1
- 7.1 High
CVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:H - Updated
- 2026-11-02
OSVopenSUSE-SU-2026:12420-1 No score
libsixel-bash-completion-1.10.5-3.1 on GA media
These are all security issues fixed in the libsixel-bash-completion-1.10.5-3.1 package on the GA media of openSUSE Tumbleweed.
- Record
openSUSE-SU-2026:12420-1- Updated
- 2026-11-05
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
libsixelDebian:12 |
All versions, plus listed versions 1.10.3-31.10.5-11:1.8.7-11:1.8.7-21:1.8.7-3 Show 4 moreShow less1:1.8.7-41:1.8.7-51:1.8.7-61:1.8.7-r2-1 |
None known |
libsixelDebian:13 |
All versions, plus listed versions 1.10.5-11:1.8.7-11:1.8.7-21:1.8.7-31:1.8.7-41:1.8.7-51:1.8.7-61:1.8.7-r2-1 |
None known |
libsixelDebian:14 |
before 1:1.8.7-r2-1, plus listed versions 1.10.5-11:1.8.7-11:1.8.7-21:1.8.7-31:1.8.7-41:1.8.7-51:1.8.7-6 |
1:1.8.7-r2-1 |
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 |
libsixelopenSUSE:Tumbleweed From an advisory covering 4 CVEs |
before 1.10.5-3.1 | 1.10.5-3.1 |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected | ||
| affected, aliases, facts, references | OSV | |
| first indexed | CVE List, EUVD, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-44637 is a high vulnerability (CVSS 7.1) in Saitoha Libsixel, published May 14, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.16%, the 5th percentile. Fixed in libsixel 1:1.8.7-r2-1.
References
github.com/saitoha/libsixel/security/advisories/GHSA-9jm7-77gr-qghv
github.com/CVEProject/cvelistV5/tree/main/cves/2026/44xxx/CVE-2026-44637.json
nvd.nist.gov/vuln/detail/CVE-2026-44637
security-tracker.debian.org/tracker/CVE-2026-44637
ubuntu.com/security/CVE-2026-44637
cve.org/CVERecord?id=CVE-2026-44637