CVE-2011-1926

CVE-2011-1926 is a medium-severity vulnerability in Cmu Cyrus Imap Server with a CVSS 2.0 base score of 5.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-264.

Key facts

• Severity: Medium (CVSS 2.0 base score 5.1)
• EPSS exploit prediction: 4% (89th percentile)
• Actively exploited: Not listed in CISA KEV
• Weakness: CWE-264
• Affected product: Cmu Cyrus Imap Server
• Published: 2011-05-23
• Last modified: 2026-06-16

Description

The STARTTLS implementation in Cyrus IMAP Server before 2.4.7 does not properly restrict I/O buffering, which allows man-in-the-middle attackers to insert commands into encrypted sessions by sending a cleartext command that is processed after TLS is in place, related to a "plaintext command injection" attack, a similar issue to CVE-2011-0411.

Frequently asked questions

What is CVE-2011-1926?

The STARTTLS implementation in Cyrus IMAP Server before 2.4.7 does not properly restrict I/O buffering, which allows man-in-the-middle attackers to insert commands into encrypted sessions by sending a cleartext command that is processed after TLS is in place, related to a "plaintext command injection" attack, a similar issue to CVE-2011-0411.

How severe is CVE-2011-1926?

CVE-2011-1926 has a CVSS 2.0 base score of 5.1, rated medium severity.

Is CVE-2011-1926 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 4% (89th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2011-1926?

CVE-2011-1926 primarily affects Cmu Cyrus Imap Server. In total, 35 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2011-1926?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2011-1926 published?

CVE-2011-1926 was published on 2011-05-23 and last updated on 2026-06-16.

References

• http://bugzilla.cyrusimap.org/show_bug.cgi?id=3423
• http://bugzilla.cyrusimap.org/show_bug.cgi?id=3424
• http://git.cyrusimap.org/cyrus-imapd/patch/?id=523a91a5e86c8b9a27a138f04a3e3f2d8786f162
• http://lists.fedoraproject.org/pipermail/package-announce/2011-June/061374.html
• http://lists.fedoraproject.org/pipermail/package-announce/2011-June/061415.html
• http://openwall.com/lists/oss-security/2011/05/17/15
• http://openwall.com/lists/oss-security/2011/05/17/2
• http://secunia.com/advisories/44670
• http://secunia.com/advisories/44876
• http://secunia.com/advisories/44913
• http://secunia.com/advisories/44928
• http://www.cyrusimap.org/docs/cyrus-imapd/2.4.7/changes.php
• http://www.debian.org/security/2011/dsa-2242
• http://www.debian.org/security/2011/dsa-2258
• http://www.kb.cert.org/vuls/id/555316
• http://www.mandriva.com/security/advisories?name=MDVSA-2011:100
• http://www.redhat.com/support/errata/RHSA-2011-0859.html
• http://www.securitytracker.com/id?1025625
• https://bugzilla.redhat.com/show_bug.cgi?id=705288
• https://exchange.xforce.ibmcloud.com/vulnerabilities/67867

Affected products (35)

• cpe:2.3:a:cmu:cyrus_imap_server:*:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.0.17:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.1.16:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.1.17:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.1.18:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.2.8:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.2.9:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.2.10:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.2.11:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.2.12:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.2.13:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.2.13p1:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.0:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.1:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.2:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.3:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.4:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.5:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.6:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.7:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.8:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.9:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.10:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.11:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.12:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.13:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.14:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.15:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.3.16:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.4.0:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.4.1:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.4.2:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.4.3:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.4.4:*:*:*:*:*:*:*
• cpe:2.3:a:cmu:cyrus_imap_server:2.4.5:*:*:*:*:*:*:*

More vulnerabilities in Cmu Cyrus Imap Server

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• CVE-2011-3481 — Medium (CVSS 4.3): The index_get_ids function in index.c in imapd in Cyrus IMAP Server before 2.4.11, when server-side threading is…

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