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CVE-2003-1564· NVD / CVE Program· CNA mitre

libxml2, possibly before 2.5.0, does not properly detect recursion during entity expansion, which allows context-dependent attackers to caus

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."

MediumCVSS 6.5 · v3.1—No exploit Fix available
Published
Dec 31, 2003
Updated
Jun 16, 2026
EPSS
1.6% · 75th percentile
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Report tools

JSON

Action score

26

Monitor

Low priority for now.

CVSS
26 / 40 · 6.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 1.6%

Affected systems

VendorProduct
xmlsoftlibxml2

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

  • xmlsoft libxml2before 2.5.0

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

EcosystemPackageAffected rangeFix
Red Hat:enterprise_linux:2.1::aslibxml2before 0:2.4.19-11.ent0:2.4.19-11.ent
Red Hat:enterprise_linux:2.1::aslibxml2-develbefore 0:2.4.19-11.ent0:2.4.19-11.ent
Red Hat:enterprise_linux:2.1::aslibxml2-pythonbefore 0:2.4.19-11.ent0:2.4.19-11.ent

Same product

xmlsoft: all records

Other highest-scoring records for the same primary product.

  • CVE-2008-3529Heap-based buffer overflow in the xmlParseAttValueComplex function in parser.c in libxml2 before 2.7.0 allows context-dependent attackers to
    47Plan
  • CVE-2017-7376Buffer overflow in libxml2 allows remote attackers to execute arbitrary code by leveraging an incorrect limit for port values when handling
    46Plan
  • CVE-2022-40303An issue was discovered in libxml2 before 2.10.3.
    42Plan
  • CVE-2021-3518There's a flaw in libxml2 in versions before 2.9.11.
    42Plan
  • CVE-2011-1944Integer overflow in xpath.c in libxml2 2.6.x through 2.6.32 and 2.7.x through 2.7.8, and libxml 1.8.16 and earlier, allows context-dependent
    41Plan
  • CVE-2017-7375A flaw in libxml2 allows remote XML entity inclusion with default parser flags (i.e., when the caller did not request entity substitution, D
    40Plan

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
red hat:libxml20:2.4.19-11.ent · Red Hat:enterprise_linux:2.1::asPackage registry (OSV)
red hat:libxml2-devel0:2.4.19-11.ent · Red Hat:enterprise_linux:2.1::asPackage registry (OSV)
red hat:libxml2-python0:2.4.19-11.ent · Red Hat:enterprise_linux:2.1::asPackage registry (OSV)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

No dated events beyond publication.

EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

No credits in the CNA record.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

No nightly-computed relations.

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • A user must open a link or visit a page.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
Required
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-776 · Improper Restriction of Recursive Entity References in DTDs ('XML Entity Expansion')

CVSS vector

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

nvd-primary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

—

Noroxi analysis

No Noroxi analysis for this record yet

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Change log

  1. Fix✗ → ✓

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References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records