CVE-2026-42007
Description
A flaw was found in Dovecot. An authenticated attacker can use a Sieve script with the editheader extension to trigger a use-after-free vulnerability in the mail editing code. This can lead to memory corruption, potentially crashing the mail delivery process and allowing for arbitrary code execution in the context of that process.
Statement
This flaw requires an attacker to authenticate with valid credentials before it can be exploited, and exploitation additionally depends on the Sieve editheader extension being enabled, which is not Dovecot's default configuration. Because the CVSS attack vector requires low-privileged authentication (PR:L) rather than unauthenticated remote access, and the confirmed impact is primarily memory corruption leading to a crash of the mail delivery process, this issue is rated Important rather than Critical. Disabling the Sieve editheader extension fully mitigates the vulnerability without requiring a package update.
Mitigation
To mitigate this vulnerability, disable the Sieve `editheader` extension in the Dovecot configuration. After modifying the configuration, the Dovecot service must be restarted for the changes to take effect. Disabling this extension will remove its associated functionality.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
The following CVSS metrics and score provided are preliminary and subject to review.
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 9.1 | N/A | 9.1 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Changed | N/A | Changed |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | Low | N/A | Low |
| Availability Impact | High | N/A | High |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Memory
If the expired pointer is used in a read operation, an attacker might be able to control data read in by the application.
Availability
Technical Impact: DoS: Crash, Exit, or Restart
If the expired pointer references a memory location that is not accessible to the product, or points to a location that is "malformed" (such as NULL) or larger than expected by a read or write operation, then a crash may occur.
Integrity,Confidentiality,Availability
Technical Impact: Execute Unauthorized Code or Commands
If the expired pointer is used in a function call, or points to unexpected data in a write operation, then code execution may be possible.
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