CVE-2023-40703
Denial of Service via specially crafted block fields in Mattermost Boards
Mattermost fails to properly limit the characters allowed in different fields of a block in Mattermost Boards allowing a attacker to consume excessive resources, possibly leading to Denial of Service, by patching the field of a block using a specially crafted string.
Attack profile
How easy it is to exploit
- Attack vector
- Network
- Complexity
- Low
- Privileges needed
- Low
- User interaction
- None
What an attacker can affect
- Confidentiality
- None
- Integrity
- None
- Availability
- Low
Exploit likelihood
What each source reports
CVE List Score used
Denial of Service via specially crafted block fields in Mattermost Boards
Mattermost fails to properly limit the characters allowed in different fields of a block in Mattermost Boards allowing a attacker to consume excessive resources, possibly leading to Denial of Service, by patching the field of a block using a specially crafted string.
- Record
CVE-2023-40703- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-400
- Updated
- 2026-11-02
EUVDEUVD-2023-2945
Mattermost fails to properly limit the characters allowed in different fields of a block in Mattermost Boards allowing a attacker to consume excessive resources, possibly leading to Denial of Service, by patching the field of a block using a specially crafted string.
- Record
EUVD-2023-2945- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L - Updated
- 2026-11-02
GitHub AdvisoriesGHSA-c37r-v8jx-7cv2
Mattermost Uncontrolled Resource Consumption vulnerability
Mattermost fails to properly limit the characters allowed in different fields of a block in Mattermost Boards allowing a attacker to consume excessive resources, possibly leading to Denial of Service, by patching the field of a block using a specially crafted string.
- Record
GHSA-c37r-v8jx-7cv2- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-400
- Updated
- 2026-11-02
NVD
Mattermost fails to properly limit the characters allowed in different fields of a block in Mattermost Boards allowing a attacker to consume excessive resources, possibly leading to Denial of Service, by patching the field of a block using a specially crafted string.
- Record
CVE-2023-40703- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L - CVSS 3.1
- 7.5 High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H - Weakness
- CWE-400
- Updated
- 2026-11-02
OSV
Denial of Service via specially crafted block fields in Mattermost Boards
Mattermost fails to properly limit the characters allowed in different fields of a block in Mattermost Boards allowing a attacker to consume excessive resources, possibly leading to Denial of Service, by patching the field of a block using a specially crafted string.
- Record
CVE-2023-40703- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-400
- Updated
- 2026-11-02
OSVGHSA-c37r-v8jx-7cv2
Mattermost Uncontrolled Resource Consumption vulnerability
Mattermost fails to properly limit the characters allowed in different fields of a block in Mattermost Boards allowing a attacker to consume excessive resources, possibly leading to Denial of Service, by patching the field of a block using a specially crafted string.
- Record
GHSA-c37r-v8jx-7cv2- CVSS 3.1
- 4.3 Medium
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L - Weakness
- CWE-400
- Updated
- 2026-11-02
Affected products
Affected packages
| Package | Affected | Fixed |
|---|---|---|
github.com/mattermost/mattermost/server/v8Go |
9.1.0 up to 9.1.1 | 9.1.1 |
github.com/mattermost/mattermost/server/v8Go |
9.0.0 up to 9.0.2 | 9.0.2 |
github.com/mattermost/mattermost/server/v8Go |
before 8.1.4 | 8.1.4 |
github.com/mattermost/mattermost-server/v6Go |
before 7.8.13 | 7.8.13 |
History
| Recorded | Changed | Sources |
|---|---|---|
| first indexed | CVE List, EUVD, GitHub Advisories, NVD, OSV |
Dates are when Every CVE recorded each change. Upstream dates may differ.
In short
CVE-2023-40703 is a medium vulnerability (CVSS 4.3) in Mattermost, published November 27, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.72%, the 54th percentile. Fixed in github.com/mattermost/mattermost/server/v8 9.1.1.