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CVE-2022-25236

expat: Namespace-separator characters in "xmlns[:prefix]" attribute values can lead to arbitrary code execution

xmlparse.c in Expat (aka libexpat) before 2.4.5 allows attackers to insert namespace-separator characters into namespace URIs.

CVSS 3.1 · 9.8 Critical EPSS 35.3% KEV · Not listed
Vendors
Debian Libexpat Project Oracle and 2 more
Products
Debian Linux Libexpat Http Server and 8 more
CVE-2022-25235

expat: Malformed 2- and 3-byte UTF-8 sequences can lead to arbitrary code execution

xmltok_impl.c in Expat (aka libexpat) before 2.4.5 lacks certain validation of encoding, such as checks for whether a UTF-8 character is valid in a certain context.

CVSS 3.1 · 9.8 Critical EPSS 5.0% KEV · Not listed
Vendors
Debian Fedoraproject Libexpat Project and 3 more
Products
Debian Linux Fedora Libexpat and 9 more
CVE-2021-45960

expat: Large number of prefixed XML attributes on a single tag can crash libexpat

In Expat (aka libexpat) before 2.4.3, a left shift by 29 (or more) places in the storeAtts function in xmlparse.c can lead to realloc misbehavior (e.g., allocating too few bytes, or only freeing memory).

CVSS 3.1 · 8.8 High EPSS 4.7% KEV · Not listed
Vendors
Debian Libexpat Project Netapp and 3 more
Products
Debian Linux Libexpat Active Iq Unified Manager and 7 more
CVE-2019-15903

expat: heap-based buffer over-read via crafted XML input

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.

CVSS 3.1 · 6.5 Medium EPSS 6.6% KEV · Not listed
Vendors
Libexpat Project Python Redhat
Products
Libexpat Python Enterprise Linux and 2 more
CVE-2018-20843

expat: large number of colons in input makes parser consume high amount of resources, leading to DoS

In libexpat in Expat before 2.2.7, XML input including XML names that contain a large number of colons could make the XML parser consume a high amount of RAM and CPU resources while processing (enough to be usable for denial-of-service attacks).

CVSS 3.1 · 7.5 High EPSS 7.1% KEV · Not listed
Vendors
Canonical Debian Fedoraproject and 5 more
Products
Ubuntu Linux Debian Linux Fedora and 9 more
CVE-2013-0340

expat: internal entity expansion

expat before version 2.4.0 does not properly handle entities expansion unless an application developer uses the XML_SetEntityDeclHandler function, which allows remote attackers to cause a denial of service (resource consumption), send HTTP requests to intranet servers, or read arbitrary files via a crafted XML document, aka an XML External Entity (XXE) issue. NOTE: it could be argued that because expat already provides the ability to disable external entity expansion, the responsibility for resolving this issue lies with application developers; according to this argument, this entry should be REJECTed, and each affected application would need its own CVE.

CVSS 2.0 · 6.8 Medium EPSS 19.4% KEV · Not listed
Vendors
Apple Libexpat Project Python
Products
Ipados Iphone Os Macos and 4 more
CVE-2017-9233

expat: Inifinite loop due to invalid XML in external entity

XML External Entity vulnerability in libexpat 2.2.0 and earlier (Expat XML Parser Library) allows attackers to put the parser in an infinite loop using a malformed external entity definition from an external DTD.

CVSS 3.1 · 7.5 High EPSS 8.7% KEV · Not listed
Vendors
Debian Libexpat Project Python
Products
Debian Linux Libexpat Python
CVE-2016-4472

expat: Undefined behavior and pointer overflows

The overflow protection in Expat is removed by compilers with certain optimization settings, which allows remote attackers to cause a denial of service (crash) or possibly execute arbitrary code via crafted XML data. NOTE: this vulnerability exists because of an incomplete fix for CVE-2015-1283 and CVE-2015-2716.

CVSS 3.1 · 8.1 High EPSS 11.9% KEV · Not listed
Vendors
Canonical Libexpat Project Mcafee and 1 more
Products
Ubuntu Linux Libexpat Policy Auditor and 1 more
CVE-2016-0718

expat: Out-of-bounds heap read on crafted input causing crash

Expat allows context-dependent attackers to cause a denial of service (crash) or possibly execute arbitrary code via a malformed input document, which triggers a buffer overflow.

CVSS 3.1 · 9.8 Critical EPSS 13.3% KEV · Not listed
Vendors
Apple Canonical Debian and 7 more
Products
Mac Os X Ubuntu Linux Debian Linux and 13 more
CVE-2026-76641

Expat Out-of-Bounds Read via dtdCopy

Expat through 2.8.3 contains an out-of-bounds read vulnerability that allows attackers to trigger memory corruption by processing XML with external entity parsers created via XML_ExternalEntityParserCreate. A struct size mismatch between ELEMENT_TYPE members causes storeAtts to read the attIndex member past allocated memory boundaries, resulting in failure to normalize whitespace in non-CDATA attributes or a wild pointer dereference causing a segfault. This vulnerability was introduced by the fix for CVE-2026-66046.

CVSS 4.0 · 8.7 High EPSS < 1% KEV · Not listed
Vendors
Libexpat Libexpat Project
Products
Expat Libexpat