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.

Published: 2011-05-23 Last update: 2026-04-29 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2011-1926 is rated Moderate Risk (46.4/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 4.87%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2011-1926

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2025-03-30 9.95% 4.87% -5.09%
2 2025-03-29 4.87% 9.95% +5.09%
3 2025-03-25 — 4.87% —

Full EPSS history (7 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2011-1926

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.1 2.0 MEDIUM
AV:N/AC:H/Au:N/C:P/I:P/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:H)
Exploitation requires uncommon or highly specific conditions.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:P)
Partial confidentiality impact.
Integrity impact (I:P)
Partial integrity impact.
Availability impact (A:P)
Partial availability impact.
 4.9 6.4 [email protected]

Weakness enumeration for CVE-2011-1926

OS Trackers for CVE-2011-1926

vendor priority summary link
redhat medium — https://access.redhat.com/security/cve/CVE-2011-1926
ubuntu high CVE-2011-1926 high priority: Ubuntu including 2 source packages (cyrus-imapd-2.2, cyrus-imapd-2.4), 20 status rows across 10 suites (dapper, hardy, lucid, maverick, natty, oneiric, precise, quantal, raring, upstream): DNE 8, ignored 4, not-affected 4, released 4. https://ubuntu.com/security/CVE-2011-1926

Affected software / configurations for CVE-2011-1926

Vendor Product Version Raw CPE
cmu cyrus_imap_server <= 2.4.6 cpe:2.3:a:cmu:cyrus_imap_server:*:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.0.17 cpe:2.3:a:cmu:cyrus_imap_server:2.0.17:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.1.16 cpe:2.3:a:cmu:cyrus_imap_server:2.1.16:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.1.17 cpe:2.3:a:cmu:cyrus_imap_server:2.1.17:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.1.18 cpe:2.3:a:cmu:cyrus_imap_server:2.1.18:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.2.8 cpe:2.3:a:cmu:cyrus_imap_server:2.2.8:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.2.9 cpe:2.3:a:cmu:cyrus_imap_server:2.2.9:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.2.10 cpe:2.3:a:cmu:cyrus_imap_server:2.2.10:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.2.11 cpe:2.3:a:cmu:cyrus_imap_server:2.2.11:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.2.12 cpe:2.3:a:cmu:cyrus_imap_server:2.2.12:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.2.13 cpe:2.3:a:cmu:cyrus_imap_server:2.2.13:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.2.13p1 cpe:2.3:a:cmu:cyrus_imap_server:2.2.13p1:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.0 cpe:2.3:a:cmu:cyrus_imap_server:2.3.0:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.1 cpe:2.3:a:cmu:cyrus_imap_server:2.3.1:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.2 cpe:2.3:a:cmu:cyrus_imap_server:2.3.2:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.3 cpe:2.3:a:cmu:cyrus_imap_server:2.3.3:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.4 cpe:2.3:a:cmu:cyrus_imap_server:2.3.4:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.5 cpe:2.3:a:cmu:cyrus_imap_server:2.3.5:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.6 cpe:2.3:a:cmu:cyrus_imap_server:2.3.6:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.7 cpe:2.3:a:cmu:cyrus_imap_server:2.3.7:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.8 cpe:2.3:a:cmu:cyrus_imap_server:2.3.8:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.9 cpe:2.3:a:cmu:cyrus_imap_server:2.3.9:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.10 cpe:2.3:a:cmu:cyrus_imap_server:2.3.10:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.11 cpe:2.3:a:cmu:cyrus_imap_server:2.3.11:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.12 cpe:2.3:a:cmu:cyrus_imap_server:2.3.12:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.13 cpe:2.3:a:cmu:cyrus_imap_server:2.3.13:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.14 cpe:2.3:a:cmu:cyrus_imap_server:2.3.14:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.15 cpe:2.3:a:cmu:cyrus_imap_server:2.3.15:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.3.16 cpe:2.3:a:cmu:cyrus_imap_server:2.3.16:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.4.0 cpe:2.3:a:cmu:cyrus_imap_server:2.4.0:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.4.1 cpe:2.3:a:cmu:cyrus_imap_server:2.4.1:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.4.2 cpe:2.3:a:cmu:cyrus_imap_server:2.4.2:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.4.3 cpe:2.3:a:cmu:cyrus_imap_server:2.4.3:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.4.4 cpe:2.3:a:cmu:cyrus_imap_server:2.4.4:*:*:*:*:*:*:*
cmu cyrus_imap_server 2.4.5 cpe:2.3:a:cmu:cyrus_imap_server:2.4.5:*:*:*:*:*:*:*

References for CVE-2011-1926

URL Tags
http://bugzilla.cyrusimap.org/show_bug.cgi?id=3423 Patch
http://bugzilla.cyrusimap.org/show_bug.cgi?id=3424 Patch
http://git.cyrusimap.org/cyrus-imapd/patch/?id=523a91a5e86c8b9a27a138f04a3e3f2d8786f162 Patch
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 Patch
http://openwall.com/lists/oss-security/2011/05/17/2 Patch
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 US Government Resource
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 Patch
https://exchange.xforce.ibmcloud.com/vulnerabilities/67867
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