CVE-2011-1756

modules/xmpp/serv_xmpp.c in Citadel 7.86 and earlier does not properly detect recursion during entity expansion, which allows remote attackers to cause a denial of service (memory and CPU consumption) via a crafted XML document containing a large number of nested entity references, a similar issue to CVE-2003-1564.

Published: 2011-06-21 Last update: 2026-04-29 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2011-1756 is rated Moderate Risk (50.5/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 2.66%). EPSS rose +1.20% over the last day, indicating growing attacker interest. 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-2011-1756

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 2026-06-15 1.46% 2.66% +1.20%
2 2025-03-30 1.77% 1.46% -0.31%
3 2025-03-29 — 1.77% —

Full EPSS history (7 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2011-1756

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
5.0 2.0 MEDIUM
AV:N/AC:L/Au:N/C:N/I:N/A:P Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:L)
Exploitation conditions are straightforward and predictable.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:N)
No confidentiality impact.
Integrity impact (I:N)
No integrity impact.
Availability impact (A:P)
Partial availability impact.
 10.0 2.9 [email protected]

Weakness enumeration for CVE-2011-1756

OS Trackers for CVE-2011-1756

vendor priority summary link
ubuntu medium CVE-2011-1756 medium priority: Ubuntu including 1 source packages (citadel), 19 status rows across 19 suites (artful, bionic, hardy, lucid, maverick, natty, oneiric, precise, quantal, raring, saucy, trusty, upstream, utopic, vivid, wily, xenial, yakkety, zesty): ignored 14, DNE 2, not-affected 2, released 1. https://ubuntu.com/security/CVE-2011-1756

Affected software / configurations for CVE-2011-1756

Vendor Product Version Raw CPE
citadel citadel <= 7.86 cpe:2.3:a:citadel:citadel:*:*:*:*:*:*:*:*
citadel citadel 7.11 cpe:2.3:a:citadel:citadel:7.11:*:*:*:*:*:*:*
citadel citadel 7.50 cpe:2.3:a:citadel:citadel:7.50:*:*:*:*:*:*:*
citadel citadel 7.60 cpe:2.3:a:citadel:citadel:7.60:*:*:*:*:*:*:*
citadel citadel 7.80 cpe:2.3:a:citadel:citadel:7.80:*:*:*:*:*:*:*
citadel citadel 7.81 cpe:2.3:a:citadel:citadel:7.81:*:*:*:*:*:*:*
citadel citadel 7.82 cpe:2.3:a:citadel:citadel:7.82:*:*:*:*:*:*:*
citadel citadel 7.84 cpe:2.3:a:citadel:citadel:7.84:*:*:*:*:*:*:*

References for CVE-2011-1756

cvelogic Threat Intelligence