high CVSS 7.5 EPSS 0.27%

CVE-2026-42392·Dovecot vulnerability

An attacker that has valid credentials can send an invalid IMAP URLFETCH command, which causes uninitialized memory to be included in the error response returned to the client. Process memory contents can be disclosed to the client, which may include sensitive data. Disable the IMAP URLAUTH functionality. Update to non-vulnerable version. No publicly available exploits are known.

Severity
high
Software
Dovecot
Fixed in
1:2.4.1+dfsg1-6+deb13u7
Published

How likely is exploitation

FIRST's Exploit Prediction Scoring System puts the probability of this CVE being exploited in the next 30 days at 0.27% — higher than 17% of all published CVEs. EPSS is an independent forecast of exploitation, not a severity rating: it says nothing about how much damage a successful attack does, which is what a CVSS score measures.

Read the two together. CVE-2026-42392 scores 7.5 on CVSS, so a successful attack would be serious — but at 0.27%, almost nobody is currently attempting it. That is a different situation from a flaw under mass exploitation, and it is usually the difference between patching on your next maintenance window and patching tonight.

Affected versions

Until: 1:2.4.1+dfsg1-6+deb13u7

Fixed in: 1:2.4.1+dfsg1-6+deb13u7

How to fix this CVE

Update Dovecot to version 1:2.4.1+dfsg1-6+deb13u7 or later to address a memory disclosure vulnerability in the IMAP URLFETCH command handler. Authenticated attackers can trigger malformed requests that leak uninitialized process memory containing potentially sensitive data. Apply the security update immediately and verify the patched version is running on all mail servers.

sudo dnf update dovecot

Defensia detects this vulnerability

How to check if you are affected

  1. Run `dovecot --version` or `dpkg -l | grep dovecot` (Debian/Ubuntu) / `rpm -qa | grep dovecot` (RHEL/CentOS) to identify the currently installed Dovecot version
  2. Check if IMAP service is enabled and listening: `sudo systemctl status dovecot` and `sudo ss -tlnp | grep -i imap`
  3. Review Dovecot configuration for URLAUTH settings in `/etc/dovecot/conf.d/` — search for `imap_urlauth` directives
  4. Verify the patch was applied by confirming version matches 1:2.4.1+dfsg1-6+deb13u7 or later with `dovecot --version`

FAQ

What is CVE-2026-42392?

CVE-2026-42392 is a memory disclosure vulnerability in Dovecot's IMAP URLFETCH implementation that allows authenticated users to craft malicious URLFETCH commands triggering uninitialized memory exposure in error responses, potentially revealing sensitive server memory contents.

Is CVE-2026-42392 being actively exploited?

No, CVE-2026-42392 is not listed on the CISA Known Exploited Vulnerabilities (KEV) catalog, and no public exploits are currently available. However, the attack requires only valid IMAP credentials, making it accessible to authorized users or those with compromised accounts.

What versions of Dovecot are affected by CVE-2026-42392?

All versions prior to 1:2.4.1+dfsg1-6+deb13u7 are affected. The vulnerability exists across Dovecot 2.4.x releases in Debian 13 and potentially earlier branches, depending on backport status.

How do I check if my server is vulnerable to CVE-2026-42392?

Run `dovecot --version` and compare the output against 1:2.4.1+dfsg1-6+deb13u7; if your version is lower, the server is vulnerable. Additionally, confirm IMAP is enabled with `sudo systemctl is-active dovecot`.

Does Defensia detect CVE-2026-42392?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Dovecot is installed on a monitored server, CVE-2026-42392 will appear in your dashboard with remediation steps.

Related Dovecot CVEs

CVE-2026-73208CVSS 9An 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.
CVE-2026-40018CVSS 9None None None No publicly available exploits are known.
CVE-2026-40019CVSS 9An 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-2026-33605CVSS 9An 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-2026-42391CVSS 9An 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.

References

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