Alibaba Cloud Linux 3 : 0327: dovecot (ALINUX3-SA-2026:0327)

critical Nessus Plugin ID 373496

Synopsis

The remote Alibaba Cloud Linux host is missing one or more security updates.

Description

The remote Alibaba Cloud Linux 3 host has packages installed that are affected by multiple vulnerabilities as referenced in the ALINUX3-SA-2026:0327 advisory.

Package updates are available for Alibaba Cloud Linux 3 that fix the following vulnerabilities:

CVE-2026-27852:
An attacker that can send mail to a user can craft a message whose headers contain a very large number of email addresses or MIME parameters, which causes excessive memory usage when the message is later parsed.
The message is still delivered, but reading it over IMAP can exhaust the memory limit of the process and terminate it, causing denial of service for the affected user. Update to non-vulnerable version. No publicly available exploits are known.

CVE-2026-33263:
When mail_max_userip_connections is set (default 10) and reached, submission-login can crash with epoll() panic caused by file descriptor handling issues. If running in high-security mode (default for community releases), only the new submission connection gets terminated. If running in high-performance mode (default for Pro releases), all connections handled by the submission-login process will be terminated.
The crashes can cause failure for user to send a message, or it can cause duplicate messages to be sent.
If TLS is not used (in the backend server processing the submission), duplicate deliveries cannot happen, because the crash can only happen at AUTH stage. Limit the number of connections handled by single submission-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.

CVE-2026-33605:
An unauthenticated attacker can crash the ManageSieve login process by sending a small malformed command before authenticating. If running in high-security mode (default for community releases), only the attacker's own connection is terminated. If running in high-performance mode (default for Pro releases), all connections handled by the same managesieve-login process are terminated. Repeating the attack can cause denial of service for Sieve script management. Restrict network access to the ManageSieve service to trusted clients. Update to non-vulnerable version. No publicly available exploits are known.

CVE-2026-40018:
None None None No publicly available exploits are known.

CVE-2026-40019:
An unauthenticated attacker can send a truncated quoted argument to the ManageSieve login process, which makes it spin in an infinite loop consuming CPU. This can cause degradation or denial of service for Sieve script management, and repeated connections can consume all available CPU on the server. Monitor system for abnormal CPU usage and kill the offending process. Restrict network access to the ManageSieve service to trusted clients. Update to non-vulnerable version. No publicly available exploits are known.

CVE-2026-42007:
An attacker that has valid credentials can use a Sieve script with the editheader extension to trigger a use-after-free in the mail editing code, and to write memory contents beyond the intended buffer into the delivered mail. This causes memory leak and opportunity to do memory corruption during mail delivery, which can crash the delivery process and may allow execution of arbitrary code in the context of that process. Disable the Sieve editheader extension. Update to non-vulnerable version. No publicly available exploits are known.

CVE-2026-42391:
An unauthenticated attacker can send an IMAP ID command with a very large number of parameters before logging in, which causes memory and CPU usage to grow disproportionately. The login process can be terminated by the out-of-memory handling, which also terminates all other connections handled by the same process. This can cause degradation or denial of service for IMAP logins. Limit the number of connections handled by a single imap-login process. This has a performance impact though. Update to non-vulnerable version. No publicly available exploits are known.

CVE-2026-73208:
An attacker that holds a token intended for a different purpose can authenticate, because when an OAuth2 token response does not contain a scope claim, the audience claim is used in its place and checked against the configured required scopes. These are different concepts, and the audience claim does not describe what a token is allowed to do. A token that grants no relevant permissions can be accepted because its intended recipient value happens to match a configured scope name, granting access that should have been denied. It also hides an identity provider misconfiguration where scopes are not being issued at all.
Ensure the identity provider issues a scope claim for all tokens used with Dovecot, and that configured scope names do not match audience values. Update to non-vulnerable version. No publicly available exploits are known.

Tenable has extracted the preceding description block directly from the Alibaba Cloud Linux security advisory.

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

Solution

Update the affected packages.

Plugin Details

Severity: Critical

ID: 373496

File Name: alinux3_sa_2026-0327.nasl

Version: 1.1

Type: Local

Family: Alibaba Cloud Linux Local Security Checks

Published: 10/29/2026

Updated: 10/29/2026

Supported Sensors: Nessus

Risk Information

VPR

Risk Factor: Medium

Score: 4.4

Percentile: 57.77

CVSS v2

Risk Factor: High

Base Score: 8

Temporal Score: 5.9

Vector: CVSS2#AV:N/AC:L/Au:S/C:P/I:P/A:C

CVSS Score Source: CVE-2026-42007

CVSS v3

Risk Factor: Critical

Base Score: 9.1

Temporal Score: 7.9

Vector: CVSS:3.0/AV:N/AC:L/PR:L/UI:N/S:C/C:L/I:L/A:H

Temporal Vector: CVSS:3.0/E:U/RL:O/RC:C

Vulnerability Information

CPE: cpe:/o:alibabacloud:alibaba_cloud_linux_3, p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:dovecot-devel, p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:dovecot-mysql, p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:dovecot-pgsql, p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:dovecot-pigeonhole, p-cpe:/a:alibabacloud:alibaba_cloud_linux_3:dovecot

Required KB Items: Host/local_checks_enabled, Host/cpu, Host/Alibaba/release, Host/Alibaba/rpm-list

Exploit Ease: No known exploits are available

Patch Publication Date: 10/28/2026

Vulnerability Publication Date: 8/28/2026

Reference Information

CVE: CVE-2026-27852, CVE-2026-33263, CVE-2026-33605, CVE-2026-40018, CVE-2026-40019, CVE-2026-42007, CVE-2026-42391, CVE-2026-73208

Detections

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