Security readout for executives and security teams
Plain-English summary
A user with valid mail credentials may abuse Dovecot’s Sieve editheader feature to corrupt memory during mail delivery. Successful exploitation could crash delivery services and may permit code execution under the delivery process account. The flaw is critical, but authentication and the vulnerable extension are required.
Executive priority
Treat as an urgent remediation for exposed mail systems. Disable editheader promptly, identify affected deployments, and schedule vendor-confirmed upgrades. Prioritize environments where many users or externally authenticated accounts can manage Sieve scripts. Current evidence does not establish active exploitation.
Technical view
CVE-2026-42007 is a CWE-416 use-after-free in mail editing triggered by a Sieve script using editheader. It can expose memory beyond an intended buffer, corrupt memory, crash mail delivery, and potentially enable arbitrary code execution. CVSS 3.1 is 9.1: network-accessible, low complexity, low privileges, no user interaction, and changed scope.
Likely exposure
Exposure is limited to affected OX Dovecot Pro or CE versions where authenticated users can submit Sieve scripts and editheader is enabled. The bundle lists Pro 2.3.0, 3.0.0, and 3.1.0, plus CE 2.3.0. Exact fixed releases are not provided.
Exploitation context
The supplied sources report no publicly available exploits, and the CVE is not identified as CISA KEV. Exploitation nevertheless requires only valid credentials, low complexity, and no victim interaction. Compromised or malicious mail accounts could therefore present a credible internal or authenticated remote threat.
Researcher notes
The described primitive combines use-after-free, unintended memory disclosure into delivered mail, and possible memory corruption. Code execution is described as possible, not confirmed. The source bundle does not identify fixed version numbers, exploit artifacts, or observed attacks, so validation should focus on version, feature enablement, Sieve permissions, and delivery-process anomalies.
Mitigation direction
- Disable the Sieve editheader extension immediately where operationally feasible.
- Update affected systems to a vendor-confirmed non-vulnerable version.
- Review the Open-Xchange advisory for exact fixed releases and supported upgrade paths.
- Restrict Sieve script access until remediation is verified.
Validation and detection
- Inventory OX Dovecot Pro and CE deployments and record their exact versions.
- Confirm whether the Sieve editheader extension is enabled on each deployment.
- Determine which authenticated accounts can create or modify Sieve scripts.
- Verify upgraded versions against the Open-Xchange advisory.
- Review mail-delivery crashes or abnormal process behavior around suspicious Sieve activity.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-416: Exact CWE lookup
Use the exact CWE identifier as the starting point before reviewing related ATT&CK behavior. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupExecution behavior lookup
The CVE wording references code or command execution, so execution technique review may help defensive triage. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-42007 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Critical
- CVSS
- 9.1 (3.1)
- Known Exploited
- No
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H3.15.3OXVulnerability scoring details
Base CVSS 3.1 score
9.1CriticalVector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
Vulnerability timeline
Timeline events are normalized from CVE metadata, CNA source timelines, ADP timelines, and KEV metadata when present.
- CVE reservedCVE Program
The CVE ID was reserved by the assigning CNA.
- CVE publishedCVE Program
The CVE record was published.
- CVE updatedCVE Program
The CVE record metadata indicates this as the latest update time.
Source materials
- CVE List V5 sourceCVE List V5
- https://documentation.open-xchange.com/dovecot/security/advisories/csaf/2026/oxdc-adv-2026-0003.jsonCVE reference, OX · vendor-advisory
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Use After Free
Use After Free represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.