CVE-2024-1402· NVD / CVE Program· CNA Mattermost

Denial of service in mattermost mobile apps and server via emoji reactions

Noroxi assessment

Priority: Monitor (action score 17/100)

The sources we track (CISA KEV, Exploit-DB, Metasploit, Nuclei, GitHub) show no public exploit code or exploitation in the wild.
Probability of exploitation in the next 30 days: 0.52% (FIRST EPSS).
Anyone who can reach it over the internet can trigger it. No account or password is required. A user must open a link or visit a page. No special conditions are required; it is repeatable.
Fixed version: github.com/mattermost/mattermost-server (Go) 9.1.5+incompatible, 9.2.4+incompatible; github.com/mattermost/mattermost/server/v8 (Go) 9.1.5, 9.2.4, 8.1.8.

Low priority for now. Upgrade to github.com/mattermost/mattermost-server (Go) 9.1.5+incompatible, 9.2.4+incompatible; github.com/mattermost/mattermost/server/v8 (Go) 9.1.5, 9.2.4, 8.1.8 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

Mattermost fails to check if a custom emoji reaction exists when sending it to a post and to limit the amount of custom emojis allowed to be added in a post, allowing an attacker sending a huge amount of non-existent custom emojis in a post to crash the mobile app of a user seeing the post and to crash the server due to overloading when clients attempt to retrive the aforementioned post.

MediumCVSS 4.3 · v3.1—No exploit Fix available

Published: Feb 9, 2024
Updated: Jun 17, 2026
EPSS: 0.5% · 43th percentile
CWE: CWE-400

Report tools

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Action score

Monitor

Low priority for now.

CVSS: 17 / 40 · 4.3 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 0 / 30 · 0.5%

CISA SSVC decision

Exploitation: none
Automatable: no
Technical impact: partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD: 4.3
CNA · Mattermost: 4.3; agree

CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

The score given by the assigning authority versus NVD’s independent score. A gap means the severity is contested.

Get told when this record changes

Not in KEV: no record of exploitation in the wild
No public exploit code on record
A fix has been released

If any of these changes, we'll tell you in the daily email digest.

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Noroxi analysis

What does it mean in your environment?

The assessment above is generated automatically from the record's data; it doesn't know your environment. Our team verifies on your systems whether this vulnerability is actually exploitable and which mitigation is enough.

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Affected systems

Is your version affected?

Pick the product and type the version you run. It's compared with this record's version ranges in your browser; the version isn't sent anywhere.

Vendor	Product	CPE
mattermost	mattermost server	cpe:2.3:a:mattermost:mattermost_server

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

mattermost mattermost serverup to 8.1.7 inclusive
mattermost mattermost server9.0.0 and later · up to 9.1.4 inclusive
mattermost mattermost server9.2.0 and later · up to 9.2.3 inclusive

Versions reported by the vendor

Affected version ranges reported by the assigning authority (Mattermost). Independent of NVD's CPE analysis and usually ahead of it.

Mattermost Mattermost
- 9.3.0, 9.2.4, 9.1.5, 8.1.8not affected
- up to and including 8.1.7affected · semver
- up to and including 9.1.4affected · semver
- up to and including 9.2.3affected · semver

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Go	github.com/mattermost/mattermost-server	from 9.1.0+incompatible · before 9.1.5+incompatible	9.1.5+incompatible
Go	github.com/mattermost/mattermost-server	from 9.2.0+incompatible · before 9.2.4+incompatible	9.2.4+incompatible
Go	github.com/mattermost/mattermost-server/v5	from 0	—
Go	github.com/mattermost/mattermost-server/v6	from 0	—
Go	github.com/mattermost/mattermost/server/v8	from 0	—
Go	github.com/mattermost/mattermost/server/v8	from 9.1.0 · before 9.1.5	9.1.5
Go	github.com/mattermost/mattermost/server/v8	from 9.2.0 · before 9.2.4	9.2.4
Go	github.com/mattermost/mattermost/server/v8	before 8.1.8	8.1.8

Same product

mattermost: all records

Other highest-scoring records for the same primary product.

CVE-2026-4858Path traversal in integration action URL leading to arbitrary API execution via system admin’s auth token.
39Monitor
CVE-2025-12421Account Takeover via Code Exchange Endpoint
39Monitor
CVE-2025-12419Account takeover on OAuth/OpenID-enabled servers
39Monitor

Published before and after this one in the same product

← EarlierCVE-2024-24774Feb 9, 2024 · Missing authorization allows users to access arbitrary security levels on Jira through webhooks (Jira Plugin)
16Monitor
← EarlierCVE-2024-24776Feb 9, 2024 · Incorrect Authorization leads to Channel Member Count Leak
17Monitor
Later →CVE-2024-1887Feb 29, 2024 · Public channel post content accessible without membership when compliance export is enabled
17Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Go:github.com/mattermost/mattermost-server	9.1.5+incompatible	Package registry (OSV)
Go:github.com/mattermost/mattermost-server	9.2.4+incompatible	Package registry (OSV)
Go:github.com/mattermost/mattermost/server/v8	8.1.8	Package registry (OSV)
Go:github.com/mattermost/mattermost/server/v8	9.1.5	Package registry (OSV)
Go:github.com/mattermost/mattermost/server/v8	9.2.4	Package registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Gian Klug (coderion)finder

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

CVE-2023-4584759 days apartPlaybook Plugin Crash via Run Checklist
30Monitor
CVE-2023-5330123 days apartDenial of Service via Opengraph Data Cache
30Monitor
CVE-2024-2498820 days apartExcessive resource consumption when sending long emoji names in user custom status
26Monitor
CVE-2024-2805335 days apartResource Exhaustion via the Invitation Feature
26Monitor
CVE-2024-2894956 days apartDoS via a large number of User Preferences
26Monitor
CVE-2023-4980959 days apartTodo plugin gets crashed and disabled by member
26Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

Mattermost Public Bug Bounty Engagement Bugcrowd · paid · up to $2,000

The product’s vendor appears in a public program. Matched by name; verify the scope text in the program.

Technical details

Attack conditions

Anyone who can reach it over the internet can trigger it.
No account or password is required.
A user must open a link or visit a page.
No special conditions are required; it is repeatable.

If successful

Confidentiality: none
Integrity: none
Availability: low · the service can be disrupted

Attack vector: Network
Attack complexity: Low
Privileges required: None
User interaction: Required
Scope: Unchanged
Confidentiality impact: None
Integrity impact: None
Availability impact: Low

Weakness class (CWE)

CWE-400 · Uncontrolled Resource Consumption

CVSS vector

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L

nvd-primary

Root cause

Code that parses nested structures sets no depth or size limit. A small input can turn into a disproportionate processing load.

The bug in code

The whole CWE-400 class

A representative example of this vulnerability class. Not the vendor's source code; it shows the faulty pattern and its fix.

Vulnerable

1function expand(node) {
2  return node.children.map(expand);
3}

Fixed

1const MAX_DEPTH = 32;
2function expand(node, depth = 0) {
3  if (depth > MAX_DEPTH) throw new Error("too deep");
4  return node.children.map((c) => expand(c, depth + 1));
5}

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

Attack patterns (CAPEC)

ATT&CK techniques

Endpoint Denial of ServiceT1499

Change log

Fix✗ → ✓Sep 28, 2026, 10:46 PM UTC

For records you follow, these changes also arrive as notifications. →

References

mattermost.com/security-updates

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records