high CVSS 8 EPSS 0.40%

CVE-2026-73209·Dovecot vulnerability

An attacker that has valid credentials can send crafted compressed data that causes the affected process to exhaust its stack and crash. The affected process is terminated, which can cause degradation or denial of service for IMAP. 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 0.40% — higher than 32% 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-2026-73209 scores 8 on CVSS, so a successful attack would be serious — but at 0.40%, 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

Organizations running Dovecot should upgrade to version 1:2.4.1+dfsg1-6+deb13u7 or later to address a stack exhaustion vulnerability that impacts IMAP availability. Authenticated attackers can exploit this flaw by sending specially crafted compressed data that causes the Dovecot process to crash, resulting in service interruption. Prioritize this update for mail servers handling production email traffic, as successful exploitation directly impacts user access to IMAP services.

sudo dnf update dovecot dovecot-imapd

Defensia detects this vulnerability

How to check if you are affected

  1. Check installed Dovecot version: dovecot --version or rpm -qa | grep dovecot
  2. Verify IMAP service is listening: ss -tlnp | grep :143 or ss -tlnp | grep :993 for IMAPS
  3. Review Dovecot logs for repeated crashes: grep -i 'Fatal\|Crash\|Signal' /var/log/dovecot/dovecot.log or journalctl -u dovecot -p err
  4. Confirm patch application by checking version matches 1:2.4.1+dfsg1-6+deb13u7 or later: dovecot --version

FAQ

What is CVE-2026-73209?

This vulnerability allows authenticated users with valid credentials to send malformed compressed data to Dovecot's IMAP service, triggering a stack overflow condition that crashes the mail server process and denies service to legitimate users.

Is CVE-2026-73209 being actively exploited?

No active exploitation has been reported. This vulnerability is not listed in CISA's Known Exploited Vulnerabilities catalog, and no public exploit code is currently available.

What versions of Dovecot are affected by CVE-2026-73209?

All versions of Dovecot up to and including 1:2.4.1+dfsg1-6+deb13u6 are vulnerable. The fix is available in version 1:2.4.1+dfsg1-6+deb13u7 and later.

How do I check if my server is vulnerable to CVE-2026-73209?

Run 'dovecot --version' to retrieve your installed version, then compare it against 1:2.4.1+dfsg1-6+deb13u7. If your version is older, your system is vulnerable.

Does Defensia detect CVE-2026-73209?

Yes — Defensia's CVE advisory scanner compares installed package versions against the NVD database. If Dovecot is installed on a monitored server, CVE-2026-73209 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-2026-33605CVSS 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-2026-40019CVSS 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-2026-27852CVSS 9An 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.

References

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