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NVD / CVE Program· CNA Mattermost

CVE-2025-27936: Webhook Secret Exposure via Timing attack in MSteams plugin

Noroxi assessment

Priority: Monitor (action score 23/100)

  • 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: 0.34% (FIRST EPSS).
  • Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. Special conditions such as timing or configuration are required.
  • Fixed version: github.com/mattermost/mattermost-plugin-msteams (Go) 2.1.0; github.com/mattermost/mattermost-server (Go) 10.5.2+incompatible; github.com/mattermost/mattermost/server/v8 (Go) 10.5.2, 8.0.0-20250314142426-c049748b8863, 8.0.0-20250218121836-2b5275d87136.

Low priority for now. Upgrade to github.com/mattermost/mattermost-plugin-msteams (Go) 2.1.0; github.com/mattermost/mattermost-server (Go) 10.5.2+incompatible; github.com/mattermost/mattermost/server/v8 (Go) 10.5.2, 8.0.0-20250314142426-c049748b8863, 8.0.0-20250218121836-2b5275d87136 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 Plugin MSTeams versions <2.1.0 and Mattermost Server versions 10.5.x <=10.5.1 with the MS Teams plugin enabled fail to perform constant time comparison on a MSTeams plugin webhook secret which allows an attacker to retrieve the webhook secret of the MSTeams plugin via a timing attack during webhook secret comparison.

MediumCVSS 5.9 · v3.1—No exploit Fix available
Published
Apr 16, 2025
Updated
Jun 17, 2026
EPSS
0.3% · 28th percentile

Report tools

JSON

Action score

23

Monitor

Low priority for now.

CVSS
23 / 40 · 5.9 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.3%

CISA SSVC decision

Exploitation
none
Automatable
no
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

CNA vs NVD score

NVD
5.9
CNA · Mattermost
5.3
0.6 point gap

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

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.

Follow CVE-2025-27936

When you'll hear from us

  • when it enters CISA KEV
  • when exploit code appears or is weaponized
  • when the record is updated (including a fixed version)
  • when EPSS rises 20 points in a week

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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.

VendorProduct
mattermostmattermost server
mattermostms teams

Affected versions

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

  • mattermost mattermost serverbefore 10.5.2
  • mattermost ms teamsbefore 2.1.0

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

    • 10.6.0, 10.5.2not affected
    • 10.5.0 and later · up to and including 10.5.1affected · semver

Package-level exposure

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

EcosystemPackageAffected rangeFix
Gogithub.com/mattermost/mattermost-plugin-msteamsfrom 0—
Gogithub.com/mattermost/mattermost-plugin-msteamsbefore 2.1.02.1.0
Gogithub.com/mattermost/mattermost-serverfrom 10.5.0+incompatible · before 10.5.2+incompatible10.5.2+incompatible
Gogithub.com/mattermost/mattermost-server/v5from 0—
Gogithub.com/mattermost/mattermost-server/v6from 0—
Gogithub.com/mattermost/mattermost/server/v8from 10.5.0 · before 10.5.210.5.2
Gogithub.com/mattermost/mattermost/server/v8before 8.0.0-20250314142426-c049748b88638.0.0-20250314142426-c049748b8863
Gogithub.com/mattermost/mattermost/server/v8before 8.0.0-20250218121836-2b5275d871368.0.0-20250218121836-2b5275d87136
openSUSE:Tumbleweedgovulncheck-vulndbbefore 0.0.20250422T181640-1.10.0.20250422T181640-1.1

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-2025-27538Apr 16, 2025 · MFA Enforcement Bypass Allows Unauthorized Removal of MFA for Other Users
    10Monitor
  • ← EarlierCVE-2025-27571Apr 16, 2025 · Channel metadata visible in archived channels despite configuration setting
    17Monitor
  • Later →CVE-2025-31363Apr 16, 2025 · Data exfiltration via AI plugin Jira tool
    26Monitor

Remediation

Which version to upgrade to

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

Product / packageFixed versionSource
Go:github.com/mattermost/mattermost-plugin-msteams2.1.0Package registry (OSV)
Go:github.com/mattermost/mattermost-server10.5.2+incompatiblePackage registry (OSV)
Go:github.com/mattermost/mattermost/server/v810.5.2Package registry (OSV)
Go:github.com/mattermost/mattermost/server/v88.0.0-20250218121836-2b5275d87136Package registry (OSV)
Go:github.com/mattermost/mattermost/server/v88.0.0-20250314142426-c049748b8863Package registry (OSV)
opensuse:govulncheck-vulndb0.0.20250422T181640-1.1 · openSUSE:TumbleweedPackage 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.

No history yet (it accumulates with the daily EPSS job).

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.

Variant candidates

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

  • CVE-2025-54499183 days apartInsecure string comparison enables timing attacks
    14Monitor

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

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.
  • No user action is required.
  • Special conditions such as timing or configuration are required.

If successful

Confidentiality
high · data can be read
Integrity
none
Availability
none
Attack vector
Network
Attack complexity
High
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
High
Integrity impact
None
Availability impact
None

Weakness class (CWE)

CWE-208 · Observable Timing Discrepancy

CVSS vector

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

nvd-primary

Attack context

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

Change log

  1. Fix✗ → ✓

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

References

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

All records