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Libexpat CVE-2019-15903

HIGH
Out-of-bounds Read (CWE-125)
2019-09-04 cve@mitre.org
7.5
CVSS 3.1 · NVD
View

Vulnerability Assessment

Weakness
CWE
ASVS 5.0
V15 - Secure Coding and Architecture Bounds checking, read limits
MITRE ATT&CK

1 technique across 1 tactic: Collection

The technique list with ATT&CK links and the kill-chain view is part of the Basic plan and up.

Impact

CVSS score of 7.5 (HIGH). Attack characteristics: network attack vector, low complexity, no privileges required, no user interaction not required. Public proof-of-concept exploit code is available.

Exploit ScenarioDerived

A remote attacker could read data from memory outside the intended buffer boundaries by sending crafted requests to the affected application. No authentication is required to exploit this vulnerability.

This Week Schedule remediation this week. Why: HIGH severity (CVSS 7.0-8.9).
Patch available 6.7% exploitation probability (EPSS)

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AnalysisAI

In libexpat before 2.2.8, crafted XML input could fool the parser into changing from DTD parsing to document parsing too early; a consecutive call to XML_GetCurrentLineNumber (or. Rated high severity (CVSS 7.5), this vulnerability is remotely exploitable, no authentication required, low attack complexity. Public exploit code available.

RemediationAI

A vendor patch is available. Apply the latest security update as soon as possible. Validate array indices and buffer lengths. Use memory-safe languages. Enable AddressSanitizer during testing.

Affects your stack

Find out whether the stacks and servers you run are on an affected version.

Checking this CVE against your own stacks and servers is part of the Basic plan and up.

Technical ContextAI · show details

This vulnerability is classified as Out-of-bounds Read (CWE-125), which allows attackers to read data from memory outside the intended buffer boundaries. In libexpat before 2.2.8, crafted XML input could fool the parser into changing from DTD parsing to document parsing too early; a consecutive call to XML_GetCurrentLineNumber (or XML_GetCurrentColumnNumber) then resulted in a heap-based buffer over-read. Affected products include: Libexpat Project Libexpat, Python. Version information: before 2.2.8.

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  • Exploit and PoC references, threat intelligence from 22 sources

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Severity by source

NVD PRIMARY 7.5 HIGH
AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Primary rating from NVD · only source for this CVE.

CVSS VectorNVD

Attack Vector
Network
Attack Complexity
Low
Privileges Required
None
User Interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

DescriptionNVD

In libexpat before 2.2.8, crafted XML input could fool the parser into changing from DTD parsing to document parsing too early; a consecutive call to XML_GetCurrentLineNumber (or XML_GetCurrentColumnNumber) then resulted in a heap-based buffer over-read.

Threat Intelligence Overview

EPSS Score
6.7%
Top 7% exploitable
Exploit
POC
Public exploit code exists
Data Quality
4 sources
Confidence: Medium

How this decision was reached

The engine reads each signal below and applies a fixed list of rules from top to bottom. The first rule that matches sets the recommended action – like a statement, every line is shown.

SignalValue
Severity HIGH
CISA KEV No
Public POC Yes
EPSS 6.7%
Patch available Yes
Active threat No
Deciding rule
HIGH severity (CVSS 7.0-8.9)
What every action level means
Emergency Immediate action required. Criteria: CRITICAL + in CISA KEV (actively exploited) without patch, OR CRITICAL + EPSS > 30% without patch, OR CRITICAL + active threat signals without patch.
Act Now Prioritize within 24-48h. Criteria: in KEV with patch available, OR CRITICAL + public POC, OR HIGH + EPSS > 10%, OR CRITICAL + active threat, OR any CRITICAL severity.
This Week Schedule remediation this week. Criteria: HIGH severity (CVSS 7.0-8.9). Patch within normal change window.
This Month Plan within 30 days. Criteria: MEDIUM severity (CVSS 4.0-6.9), lower exploitation probability. Include in regular patch cycle.
Monitor Track and reassess. Criteria: LOW severity (CVSS 0.1-3.9), minimal exploitation risk. No immediate action needed.

SSVC AssessmentENISA

SSVC Decision· derived
Scheduled
Exploitation· derived
Poc
System Exposure· derived
Open
Automatable· derived
Yes
Human Impact· derived
Medium

Priority Score

65
Low Medium High Critical
KEV: 0
EPSS: +7
CVSS: +38
PoC: +20
Weaponized: 0
Threat intel: 0
Gov advisory: 0

Attack Technique

A buffer overflow occurs when a program writes more data to a memory buffer than it was allocated to hold, causing the excess data to spill into adjacent memory regions.

Information disclosure occurs when an application unintentionally exposes sensitive data that aids attackers in reconnaissance or directly compromises security.

Affected Products (CPE)NVD

cpe:2.3:a:libexpat_project:libexpat:*:*:*:*:*:*:*:*
cpe:2.3:a:python:python:*:*:*:*:*:*:*:*
cpe:2.3:a:python:python:*:*:*:*:*:*:*:*
cpe:2.3:a:python:python:*:*:*:*:*:*:*:*
cpe:2.3:a:python:python:*:*:*:*:*:*:*:*
CVE-2022-25315 CRITICAL POC
9.8 Feb 18

In Expat (aka libexpat) before 2.4.5, there is an integer overflow in storeRawNames. Rated critical severity (CVSS 9.8),

CVE-2026-93990 HIGH POC
8.7 Sep 19

Malformed UTF-16 decoding in libexpat through 2.8.4 lets remote attackers hide XML markup from the parser: a lone high s

CVE-2022-43680 HIGH POC
7.5 Oct 24

In libexpat through 2.4.9, there is a use-after free caused by overeager destruction of a shared DTD in XML_ExternalEnti

CVE-2024-28757 HIGH POC
7.5

Alpine Linux: expat fixed in 2.6.2-r0

CVE-2017-9233 HIGH POC
7.5 Jul 25

XML External Entity vulnerability in libexpat 2.2.0 and earlier (Expat XML Parser Library) allows attackers to put the p

CVE-2025-59375 HIGH POC
7.5 Sep 15

libexpat in Expat before 2.7.2 allows attackers to trigger large dynamic memory allocations via a small document that is

CVE-2026-45186 HIGH POC
7.5 May 10

Denial of service in libexpat before 2.8.1 lets remote attackers exhaust CPU by submitting moderately sized crafted XML

CVE-2013-0340 MEDIUM POC
6.8 Jan 21

expat before version 2.4.0 does not properly handle entities expansion unless an application developer uses the XML_SetE

CVE-2016-0718 CRITICAL
9.8 May 26

Expat allows context-dependent attackers to cause a denial of service (crash) or possibly execute arbitrary code via a m

CVE-2024-45492 CRITICAL
9.8 Aug 30

An issue was discovered in libexpat before 2.6.3. Rated critical severity (CVSS 9.8), this vulnerability is remotely exp

CVE-2024-45491 CRITICAL
9.8 Aug 30

An issue was discovered in libexpat before 2.6.3. Rated critical severity (CVSS 9.8), this vulnerability is remotely exp

CVE-2026-66046 HIGH
8.7 Aug 18

Denial of service in libexpat through 2.8.3 stems from quadratic CPU complexity in the storeAtts() XML attribute process

References

Advisories & patches
PATCH https://github.com/libexpat/libexpat/commit/c20b758c332d9a13afbbb276d30db1d183a85d43 PATCH https://github.com/libexpat/libexpat/pull/318 REF http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00080.html REF http://lists.opensuse.org/opensuse-security-announce/2019-09/msg00081.html REF http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00000.html REF http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00002.html REF http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00003.html REF http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00013.html REF http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00016.html REF http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00017.html REF http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00018.html REF http://lists.opensuse.org/opensuse-security-announce/2019-11/msg00019.html REF http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00008.html REF http://lists.opensuse.org/opensuse-security-announce/2020-01/msg00040.html REF http://packetstormsecurity.com/files/154503/Slackware-Security-Advisory-expat-Updates.html REF http://packetstormsecurity.com/files/154927/Slackware-Security-Advisory-python-Updates.html REF http://packetstormsecurity.com/files/154947/Slackware-Security-Advisory-mozilla-firefox-Updates.html REF http://seclists.org/fulldisclosure/2019/Dec/23 REF http://seclists.org/fulldisclosure/2019/Dec/26 REF http://seclists.org/fulldisclosure/2019/Dec/27 REF http://seclists.org/fulldisclosure/2019/Dec/30 REF https://access.redhat.com/errata/RHSA-2019:3210 REF https://access.redhat.com/errata/RHSA-2019:3237 REF https://access.redhat.com/errata/RHSA-2019:3756 REF https://cert-portal.siemens.com/productcert/html/ssa-398330.html REF https://github.com/libexpat/libexpat/issues/342 REF https://lists.debian.org/debian-lts-announce/2019/11/msg00006.html REF https://lists.debian.org/debian-lts-announce/2019/11/msg00017.html REF https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/A4TZKPJFTURRLXIGLB34WVKQ5HGY6JJA/ REF https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/BDUTI5TVQWIGGQXPEVI4T2ENHFSBMIBP/ REF https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/S26LGXXQ7YF2BP3RGOWELBFKM6BHF6UG/ REF https://seclists.org/bugtraq/2019/Dec/17 REF https://seclists.org/bugtraq/2019/Dec/21 REF https://seclists.org/bugtraq/2019/Dec/23 REF https://seclists.org/bugtraq/2019/Nov/1 REF https://seclists.org/bugtraq/2019/Nov/24 REF https://seclists.org/bugtraq/2019/Oct/29 REF https://seclists.org/bugtraq/2019/Sep/30 REF https://seclists.org/bugtraq/2019/Sep/37 REF https://security.gentoo.org/glsa/201911-08 REF https://security.netapp.com/advisory/ntap-20190926-0004/ REF https://support.apple.com/kb/HT210785 REF https://support.apple.com/kb/HT210788 REF https://support.apple.com/kb/HT210789 REF https://support.apple.com/kb/HT210790 REF https://support.apple.com/kb/HT210793 REF https://support.apple.com/kb/HT210794 REF https://support.apple.com/kb/HT210795 REF https://usn.ubuntu.com/4132-1/ REF https://usn.ubuntu.com/4132-2/ REF https://usn.ubuntu.com/4165-1/ REF https://usn.ubuntu.com/4202-1/ REF https://usn.ubuntu.com/4335-1/ REF https://www.debian.org/security/2019/dsa-4530 REF https://www.debian.org/security/2019/dsa-4549 REF https://www.debian.org/security/2019/dsa-4571 REF https://www.oracle.com/security-alerts/cpuapr2020.html REF https://www.oracle.com/security-alerts/cpuoct2020.html REF https://www.tenable.com/security/tns-2021-11

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