CVE-2003-1564

libxml2, possibly before 2.5.0, does not properly detect recursion during entity expansion, which allows context-dependent attackers to cause a denial of service (memory and CPU consumption) via a crafted XML document containing a large number of nested entity references, aka the "billion laughs attack."

Published: 2003-12-31 Last update: 2026-06-16 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2003-1564 is rated Moderate Risk (52/100): CVSS Medium severity, with medium exploitation likelihood (EPSS 1.62%). 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-2003-1564

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 1.17% 1.62% +0.45%
2 2026-06-13 1.56% 1.17% -0.39%
3 2026-05-23 — 1.56% —

Full EPSS history (20 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2003-1564

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
6.5 3.1 MEDIUM
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:R)
A real person has to do something—click, install, enable—otherwise it doesn’t land.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 2.8 3.6 [email protected]
9.3 2.0 HIGH
AV:N/AC:M/Au:N/C:C/I:C/A:C Click to expand
Access vector (AV:N)
Can be exploited remotely over network reachability.
Access complexity (AC:M)
Exploitation needs some favorable conditions, but not exceptional ones.
Authentication (AU:N)
No authentication is required.
Confidentiality impact (C:C)
Complete confidentiality impact.
Integrity impact (I:C)
Complete integrity impact.
Availability impact (A:C)
Complete availability impact.
 8.6 10.0 [email protected]

Weakness enumeration for CVE-2003-1564

OS Trackers for CVE-2003-1564

vendor priority summary link
redhat medium — https://access.redhat.com/security/cve/CVE-2003-1564
suse medium — https://www.suse.com/security/cve/CVE-2003-1564/
ubuntu low CVE-2003-1564 low priority: Ubuntu including 1 source packages (libxml2), 6 status rows across 6 suites (hardy, lucid, natty, oneiric, precise, upstream): not-affected 5, released 1. https://ubuntu.com/security/CVE-2003-1564

Affected software / configurations for CVE-2003-1564

Vendor Product Version Raw CPE
xmlsoft libxml2 < 2.5.0 cpe:2.3:a:xmlsoft:libxml2:*:*:*:*:*:*:*:*

References for CVE-2003-1564

cvelogic Threat Intelligence