Is CVE-2026-27860 in the CISA KEV catalog?

No. CVE-2026-27860 is not currently on the CISA Known Exploited Vulnerabilities list.

What is the CVSS severity of CVE-2026-27860?

CVE-2026-27860 has a CVSS v3 base score of 3.7 (LOW).

What is the EPSS score for CVE-2026-27860?

CVE-2026-27860 has an EPSS score of 0.29% (20th percentile), estimating the probability of exploitation in the next 30 days.

How do I fix CVE-2026-27860?

Upgrade dovecot on debian 13 to 1:2.4.1+dfsg1-6+deb13u4 or later. Fixes are available for 3 affected products.

CVE & CISA-KEV Catalog

CVE-2026-27860

LOW

3.7

CVSS v3

NVD

Description

If auth_username_chars is empty, it is possible to inject arbitrary LDAP filter to Dovecot's LDAP authentication. This leads to potentially bypassing restrictions and allows probing of LDAP structure. Do not clear out auth_username_chars, or install fixed version. No publicly available exploits are known.

CWE-90

How to fix

Remediation Available

dovecotDebian

Fixed in:1:2.4.1+dfsg1-6+deb13u4CVE-2026-27860

Fixed in:1:2.4.3+dfsg1-1CVE-2026-27860

dovecotUbuntu

Fixed in:1:2.3.16+dfsg1-3ubuntu2.7USN-8136-1

Fixed in:1:2.3.21+dfsg1-2ubuntu6.3USN-8136-1

Fixed in:1:2.4.1+dfsg1-5ubuntu4.1USN-8136-1

dovecot-coreUbuntu

Fixed in:1:2.3.16+dfsg1-3ubuntu2.7USN-8136-1

Fixed in:1:2.3.21+dfsg1-2ubuntu6.3USN-8136-1

Fixed in:1:2.4.1+dfsg1-5ubuntu4.1USN-8136-1

Remediation is compiled from vendor and distribution security advisories. Always confirm against the linked source for your exact version and platform.

CVSS v3 Vector

Exploitability

Attack VectorNetwork

Attack ComplexityHigh

Privileges RequiredNone

User InteractionNone

ScopeUnchanged

Impact

ConfidentialityLow

IntegrityNone

AvailabilityNone

CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:N/A:N

Exploit Intelligence

0.29%probability of exploitation in 30 days

20thpercentile

Low risk: more likely to be exploited than 20% of all known CVEs.

References

Vendor Advisory1

documentation.open-xchange.com

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This product uses NVD data but is not endorsed or certified by the NVD. EPSS scores courtesy of FIRST.org (https://www.first.org/epss). Source: CISA KEV Catalog. Data as of 2026-04-29.