An issue was discovered in libexpat before 2.6.3. dtdCopy in xmlparse.c can have an integer overflow for nDefaultAtts on 32-bit platforms (where UINTMAX equals SIZEMAX).

Accounts. A logic issue was addressed with improved file handling.

An issue was discovered in libexpat before 2.6.3. nextScaffoldPart in xmlparse.c can have an integer overflow for mgroupSize on 32-bit platforms (where UINTMAX equals SIZEMAX).

An out-of-bounds read flaw was found in the way Expat processed certain input. A remote attacker could send specially crafted XML that, when parsed by an application using the Expat library, would cause that application to crash or, possibly, execute arbitrary code with the permission of the user running the application.

A flaw was found in expat. Passing malformed 2- and 3-byte UTF-8 sequences (for example, from start tag names) to the XML processing application on top of expat can lead to arbitrary code execution. This issue is dependent on how invalid UTF-8 is handled inside the XML processor.

A flaw was found in expat. Passing one or more namespace separator characters in the "xmlns[:prefix]" attribute values made expat send malformed tag names to the XML processor on top of expat. This issue causes arbitrary code execution depending on how unexpected cases are handled inside the XML processor.

An integer overflow was found in expat. The issue occurs in storeRawNames() by abusing the mbuffer expansion logic to allow allocations very close to INTMAX and out-of-bounds heap writes. This flaw can cause a denial of service or potentially arbitrary code execution.

defineAttribute in xmlparse.c in Expat (aka libexpat) before 2.4.3 has an integer overflow.

buildmodel in xmlparse.c in Expat (aka libexpat) before 2.4.3 has an integer overflow.

Expat (aka libexpat) before 2.4.4 has a signed integer overflow in XMLGetBuffer, for configurations with a nonzero XMLCONTEXTBYTES.

addBinding in xmlparse.c in Expat (aka libexpat) before 2.4.3 has an integer overflow.

A flaw in XML parsing could have led to a use-after-free causing a potentially exploitable crash.In official releases of Firefox this vulnerability is mitigated by wasm sandboxing; versions managed by Linux distributions may have other settings.

Expat (aka libexpat) is vulnerable to a denial of service, caused by a realloc misbehavior issue in the storeAtts function in xmlparse.c. By persuading a victim to open a specially-crafted XML content, a remote attacker could exploit this vulnerability to cause a the application to crash.

expat (libexpat) is susceptible to a software flaw that causes process interruption. When processing a large number of prefixed XML attributes on a single tag can libexpat can terminate unexpectedly due to integer overflow. The highest threat from this vulnerability is to availability, confidentiality and integrity.

expat (libexpat) is susceptible to a software flaw that causes process interruption. When processing a large number of prefixed XML attributes on a single tag can libexpat can terminate unexpectedly due to integer overflow. The highest threat from this vulnerability is to availability, confidentiality and integrity.

expat (libexpat) is susceptible to a software flaw that causes process interruption. When processing a large number of prefixed XML attributes on a single tag can libexpat can terminate unexpectedly due to integer overflow. The highest threat from this vulnerability is to availability, confidentiality and integrity.

expat (libexpat) is susceptible to a software flaw that causes process interruption. When processing a large number of prefixed XML attributes on a single tag can libexpat can terminate unexpectedly due to integer overflow. The highest threat from this vulnerability is to availability, confidentiality and integrity.

It was found that original patch for issues CVE-2015-1283 and CVE-2015-2716 used overflow checks that could be optimized out by some compilers applying certain optimization settings, which can cause the vulnerability to remain even after applying the patch.

One pattern in the fix for CVE-2015-1283/CVE-2015-2716 is:

/ bufferSize is positive here / do { bufferSize = 2; } while (bufferSize < neededSize && bufferSize > 0); if (bufferSize <= 0) { errorCode = XMLERRORNOMEMORY; return NULL;

Any of the modern optimizing compiler, IF able to infer that bufferSize is initially positive (which is true but not obvious to see through local reasoning), will eliminate bufferSize > 0 as always true when the execution is defined, and bufferSize <= 0 as always false when the execution is defined.

Without knowing that bufferSize starts positive, an optimizing compiler could also move the test bufferSize > 0 out of the loop, that is, compile the code as if it had been written:

if (bufferSize <= 0) errorCode = XMLERRORNOMEMORY; return NULL; else { do { bufferSize = 2; } while (bufferSize < neededSize); }

Both cases leads to not eliminating the vulnerability.

Upstream patch:

https://sourceforge.net/p/expat/codegit/ci/f0bec73b018caa07d3e75ec8dd967f3785d71bde/tree/expat/lib/xmlparse.c?diff=a238d7ea7a715ef3850c4cbdd86aeda7077b6bbc

In libexpat before 2.7.4, the doContent function does not properly determine the buffer size bufSize because there is no integer overflow check for tag buffer reallocation.

Last updated 24 July 2024

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).

The writeRandomBytesRtlGenRandom function in xmlparse.c in libexpat in Expat 2.2.1 and 2.2.2 on Windows allows local users to gain privileges via a Trojan horse ADVAPI32.DLL in the current working directory because of an untrusted search path, aka DLL hijacking.

libexpat is vulnerable to a denial of service, caused by improper system resource allocation. By sending a specially crafted request using an overly large token, a remote attacker could exploit this vulnerability to cause a denial of service.

libexpat could allow a remote attacker to obtain sensitive information, caused by improper handling of XML external entity (XXE) declarations by the XMLExternalEntityParserCreate function. By using a specially crafted XML content, a remote attacker could exploit this vulnerability to obtain sensitive information, and use this information to launch further attacks against the affected system.

A use-after-free flaw was found in the Expat package, caused by destruction of a shared DTD in XMLExternalEntityParserCreate in out-of-memory situations. This may lead to availability disruptions.

Accessibility. A privacy issue was addressed by removing sensitive data.

libexpat before 2.8.0 uses insufficient entropy, and thus hash flooding can occur via a crafted XML document.

In libexpat before 2.8.1, the computational complexity of attribute name collision checks allows a denial of service via moderately sized crafted XML input.

An integer overflow flaw was found in expat. This issue affects the encoding name parameter at the parser creation time, which is often hard-coded (rather than user input), takes a value in the gigabytes to trigger, and on a 64-bit machine. This flaw can cause a denial of service.

A flaw was found in expat. The vulnerability occurs due to large content in element type declarations when there is an element declaration handler present which leads to an integer overflow. This flaw allows an attacker to inject an unsigned integer, leading to a crash or a denial of service.