CVE-2026-40492
SAIL has heap buffer overflow in XWD decoder — bits_per_pixel vs pixmap_depth type confusion in byte-swap
SAIL is a cross-platform library for loading and saving images with support for animation, metadata, and ICC profiles. Prior to commit 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02, the XWD codec resolves pixel format based on pixmap_depth but the byte-swap code uses bits_per_pixel independently. When pixmap_depth=8 (BPP8_INDEXED, 1 byte/pixel buffer) but bits_per_pixel=32, the byte-swap loop accesses memory as uint32_t*, reading/writing 4x the allocated buffer size. This is a different vulnerability from the previously reported GHSA-3g38-x2pj-mv55 (CVE-2026-27168), which addressed bytes_per_line validation. Commit 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02 contains a patch.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- None
- User interaction
- None
What an attacker can affect
- Confidentiality
- High
- Integrity
- High
- Availability
- High
Exploit likelihood
What each source reports
CVE List Score used
9.8
SAIL has heap buffer overflow in XWD decoder — bits_per_pixel vs pixmap_depth type confusion in byte-swap
SAIL is a cross-platform library for loading and saving images with support for animation, metadata, and ICC profiles. Prior to commit 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02, the XWD codec resolves pixel format based on pixmap_depth but the byte-swap code uses bits_per_pixel independently. When pixmap_depth=8 (BPP8_INDEXED, 1 byte/pixel buffer) but bits_per_pixel=32, the byte-swap loop accesses memory as uint32_t*, reading/writing 4x the allocated buffer size. This is a different vulnerability from the previously reported GHSA-3g38-x2pj-mv55 (CVE-2026-27168), which addressed bytes_per_line validation. Commit 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02 contains a patch.
- Record
CVE-2026-40492- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-787
- Updated
- 2026-11-02
EUVDEUVD-2026-23644
9.8
SAIL is a cross-platform library for loading and saving images with support for animation, metadata, and ICC profiles. Prior to commit 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02, the XWD codec resolves pixel format based on pixmap_depth but the byte-swap code uses bits_per_pixel independently. When pixmap_depth=8 (BPP8_INDEXED, 1 byte/pixel buffer) but bits_per_pixel=32, the byte-swap loop accesses memory as uint32_t*, reading/writing 4x the allocated buffer size. This is a different vulnerability from the previously reported GHSA-3g38-x2pj-mv55 (CVE-2026-27168), which addressed bytes_per_line validation. Commit 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02 contains a patch.
- Record
EUVD-2026-23644- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
NVD
9.8
SAIL is a cross-platform library for loading and saving images with support for animation, metadata, and ICC profiles. Prior to commit 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02, the XWD codec resolves pixel format based on pixmap_depth but the byte-swap code uses bits_per_pixel independently. When pixmap_depth=8 (BPP8_INDEXED, 1 byte/pixel buffer) but bits_per_pixel=32, the byte-swap loop accesses memory as uint32_t*, reading/writing 4x the allocated buffer size. This is a different vulnerability from the previously reported GHSA-3g38-x2pj-mv55 (CVE-2026-27168), which addressed bytes_per_line validation. Commit 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02 contains a patch.
- Record
CVE-2026-40492- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-787
- Updated
- 2026-11-02
OSV
9.8
SAIL has heap buffer overflow in XWD decoder — bits_per_pixel vs pixmap_depth type confusion in byte-swap
SAIL is a cross-platform library for loading and saving images with support for animation, metadata, and ICC profiles. Prior to commit 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02, the XWD codec resolves pixel format based on pixmap_depth but the byte-swap code uses bits_per_pixel independently. When pixmap_depth=8 (BPP8_INDEXED, 1 byte/pixel buffer) but bits_per_pixel=32, the byte-swap loop accesses memory as uint32_t*, reading/writing 4x the allocated buffer size. This is a different vulnerability from the previously reported GHSA-3g38-x2pj-mv55 (CVE-2026-27168), which addressed bytes_per_line validation. Commit 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02 contains a patch.
- Record
CVE-2026-40492- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Weakness
- CWE-787
- Updated
- 2026-11-02
OSVDEBIAN-CVE-2026-40492
9.8
SAIL is a cross-platform library for loading and saving images with support for animation, metadata, and ICC profiles. Prior to commit 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02, the XWD codec resolves pixel format based on pixmap_depth but the byte-swap code uses bits_per_pixel independently. When pixmap_depth=8 (BPP8_INDEXED, 1 byte/pixel buffer) but bits_per_pixel=32, the byte-swap loop accesses memory as uint32_t*, reading/writing 4x the allocated buffer size. This is a different vulnerability from the previously reported GHSA-3g38-x2pj-mv55 (CVE-2026-27168), which addressed bytes_per_line validation. Commit 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02 contains a patch.
- Record
DEBIAN-CVE-2026-40492- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-02
OSVUBUNTU-CVE-2026-40492
9.8
SAIL is a cross-platform library for loading and saving images with support for animation, metadata, and ICC profiles. Prior to commit 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02, the XWD codec resolves pixel format based on pixmap_depth but the byte-swap code uses bits_per_pixel independently. When pixmap_depth=8 (BPP8_INDEXED, 1 byte/pixel buffer) but bits_per_pixel=32, the byte-swap loop accesses memory as uint32_t*, reading/writing 4x the allocated buffer size. This is a different vulnerability from the previously reported GHSA-3g38-x2pj-mv55 (CVE-2026-27168), which addressed bytes_per_line validation. Commit 36aa5c7ec8a2bb35f6fb867a1177a6f141156b02 contains a patch.
- Record
UBUNTU-CVE-2026-40492- CVSS 3.1
- 9.8 Critical
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H - Updated
- 2026-11-04
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
sailDebian:13 |
All versions, plus listed versions 0.9.10-10.9.10-20.9.10-30.9.8-10.9.8-1+deb13u10.9.9-11.2.0-1 |
None known |
sailDebian:14 |
before 0.9.10-2, plus listed versions 0.9.10-10.9.8-10.9.9-1 |
0.9.10-2 |
sailUbuntu:25.10 |
All versions, plus listed versions 0.9.7-1build10.9.8-10.9.9-1 |
None known |
sailUbuntu:26.10 |
All versions, plus listed versions 0.9.10-10.9.10-3 |
None known |
sailUbuntu:26.04:LTS |
All versions, plus listed versions 0.9.9-10.9.10-1 |
None known |
History
| Recorded | Changed | Sources |
|---|---|---|
| affected, facts | OSV | |
| first indexed | CVE List, EUVD, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2026-40492 is a critical vulnerability (CVSS 9.8) in Happyseafox Sail, published April 18, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.41%, the 35th percentile. Fixed in sail 0.9.10-2.
References
github.com/HappySeaFox/sail/security/advisories/GHSA-526v-vm72-4v64
github.com/HappySeaFox/sail/commit/36aa5c7ec8a2bb35f6fb867a1177a6f141156b02
github.com/CVEProject/cvelistV5/tree/main/cves/2026/40xxx/CVE-2026-40492.json
nvd.nist.gov/vuln/detail/CVE-2026-40492
security-tracker.debian.org/tracker/CVE-2026-40492
ubuntu.com/security/CVE-2026-40492
cve.org/CVERecord?id=CVE-2026-40492