CVE-2026-47086
Description
A flaw was found in cyrus-imapd. An authenticated user could exploit this vulnerability by minting a URLAUTH token through the GENURLAUTH command. This allows bypassing Access Control Lists (ACLs), which are rules that control access to mailboxes. Consequently, an attacker could read mail from any mailbox, even without having been granted explicit read permissions.
Statement
This flaw in cyrus-imapd allows an authenticated attacker to bypass Access Control Lists (ACLs) by minting a URLAUTH token via the GENURLAUTH command. This enables unauthorized reading of mail from any mailbox, even without explicit read permissions, posing a significant risk to data confidentiality in Red Hat deployments utilizing the Cyrus IMAP server.
Mitigation
To reduce the attack surface, restrict network access to the Cyrus IMAP server to only trusted clients and networks by configuring appropriate firewall rules. If the Cyrus IMAP service is not essential, consider disabling it. To disable the `cyrus-imapd` service, execute `sudo systemctl stop cyrus-imapd` and `sudo systemctl disable cyrus-imapd`. Disabling the service will prevent all mail access via IMAP and may require a system restart to fully take effect.
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 | 4.3 | N/A | 3.5 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | High |
| Privileges Required | Low | N/A | Low |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Changed |
| Confidentiality | Low | N/A | Low |
| Integrity Impact | None | N/A | None |
| Availability Impact | None | N/A | None |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:N/A:N
cve.org: CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:L/I:N/A:N
Understanding the Weakness (CWE)
Access Control
Technical Impact: Bypass Protection Mechanism
Access control checks for specific user data or functionality can be bypassed.
Access Control
Technical Impact: Gain Privileges or Assume Identity
Horizontal escalation of privilege is possible (one user can view/modify information of another user).
Access Control
Technical Impact: Gain Privileges or Assume Identity
Vertical escalation of privilege is possible if the user-controlled key is actually a flag that indicates administrator status, allowing the attacker to gain administrative access.
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