CVE-2026-3739Public exploitNetwork attack vector

Cross-mailbox thread disclosure via mutable access links

Published Mar 8, 2026 · Updated Mar 8, 2026

IDOR in Messages 0.2.0 allows remote authenticated users to read other users' email threads by changing a ThreadAccess link. ThreadAccessSerializer accepts PATCH updates to thread and mailbox foreign keys after permission checks validate only the record's existing thread. Any mailbox user with one accessible thread and a target thread UUID can pivot that access record and gain editor access to the target's full contents.

CVSS severity7.6
High
EPSS probability0.32%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

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Summary

What happened

IDOR in Messages 0.2.0 allows remote authenticated users to read other users' email threads by changing a ThreadAccess link. ThreadAccessSerializer accepts PATCH updates to thread and mailbox foreign keys after permission checks validate only the record's existing thread. Any mailbox user with one accessible thread and a target thread UUID can pivot that access record and gain editor access to the target's full contents.

The record

CVE
CVE-2026-3739
Published
Mar 8, 2026
Updated
Mar 8, 2026
Vendor
La Suite numérique
Product
Messages
Classifications
CWE-287, CWE-284, T1114
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Mar 8, 2026CVE publishedPublication date reported by the CVE source.
  2. Mar 8, 2026Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=0.2.0

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

La Suite numérique · Messagesversion=0.2.0

Published CVSS scores

7.6GitHub Security AdvisoryCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:H/I:L/A:N
6.5VulDBAV:N/AC:L/Au:S/C:P/I:P/A:P
6.3VulDBCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L
2.1VulDBCVSS:4.0/AV:N/AC:L/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-287Improper Authentication
CWE-284Improper Access Control
T1114Email Collection

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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