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CVE-2026-44637

libsixel: integer overflow in parser

7.1 HighFix available

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

0.16%Up 0.1 points since May 15, 2026
90%50%10%1%

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 HighCVSS: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 HighCVSS: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 HighCVSS: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 HighCVSS: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 HighCVSS: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 HighCVSS: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

Affected packages
PackageAffectedFixed
libsixel
Debian: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 less
1:1.8.7-41:1.8.7-51:1.8.7-61:1.8.7-r2-1
None known
libsixel
Debian: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
libsixel
Debian: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
libsixel
Ubuntu:16.04:LTS
All versions, plus listed versions
1.4.2-11.5.2-2
None known
libsixel
Ubuntu:18.04:LTS
All versions, plus listed versions
1.5.2-21.7.3-1
None known
libsixel
Ubuntu:20.04:LTS
All versions, plus listed versions
1.8.2-11.8.2-2.1
None known
libsixel
Ubuntu:22.04:LTS
All versions, plus listed versions
1.8.6-21.10.3-21.10.3-3
None known
libsixel
Ubuntu:24.04:LTS
All versions, plus listed versions
1.10.3-31.10.3-3build1
None known
libsixel
Ubuntu:25.10
All versions, plus listed versions
1.10.5-1
None known
libsixel
Ubuntu:26.10
All versions, plus listed versions
1.10.5-1build11:1.8.7-r2-1
None known
libsixel
Ubuntu:26.04:LTS
All versions, plus listed versions
1.10.5-11.10.5-1build1
None known
libsixel
openSUSE:Tumbleweed
From an advisory covering 4 CVEs
before 1.10.5-3.1
1.10.5-3.1

History

History
RecordedChangedSources
affected
affected, aliases, facts, referencesOSV
first indexedCVE 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

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