CVE-2022-25236 – Critical Vulnerability Discovered in xmlparse.c (Expat/libexpat) before 2.4.5: Namespace-separator Injection Attack

The recently discovered CVE-2022-25236 is a critical vulnerability affecting Expat, a popular open-source XML parser. This security flaw affects all versions of the Expat library prior to 2.4.5, and it allows attackers to inject namespace-separator characters into namespace URIs. In this article, we'll dive deep into this vulnerability – its impact, affected code snippet, and exploit details – so that affected users can take the necessary precautions and apply patches as soon as possible.

The original reference to CVE-2022-25236 can be found here: CVE-2022-25236.

Affected Code

The vulnerability revolves around the xmlparse.c component of Expat. The following snippet of vulnerable code illustrates this issue:

static XML_Bool
setContext(XML_Parser parser, const XML_Char *context) {
  ...
  for (;;) {
    int uriNameLen;
    ...
    setContext(parser, end + XML_L(" "));
    uriNameLen = dtd->defaultPrefix.binding->uriLen;
    ...
  }
}

Exploit Details

The exploit begins when an attacker crafts a specific XML document containing malicious data, including the namespace-separator character. When this document is parsed by an application using an affected version of Expat, it causes the namespace-separator character to be injected into the namespace URI. These maliciously-crafted namespace URIs can then be used by the attacker to execute further attacks or cause other unintended consequences in the targeted system.

This vulnerability becomes particularly concerning as it affects Expat, a widely-used XML parser library used in numerous applications and systems across the globe. Ensuring that these affected systems are patched is paramount to prevent possible exploitation by nefarious actors.

Mitigation Steps

To patch this vulnerability, upgrade to Expat version 2.4.5 or higher, which addresses this issue and offers improved security measures. To upgrade Expat, follow the instructions on the official Github repository: Expat GitHub Repository.

Additionally, it's crucial to ensure that all applications and systems using Expat are also updated and tested to confirm that they are no longer susceptible to this vulnerability. Regularly scanning for security vulnerabilities and keeping software up-to-date can help reduce the risks associated with cybersecurity threats such as CVE-2022-25236.

Conclusion

CVE-2022-25236 is a critical vulnerability affecting versions of Expat before 2.4.5 that allows attackers to inject namespace-separator characters into namespace URIs. By understanding the impact of this vulnerability and taking swift action to upgrade Expat to a secure version, application developers and system administrators can help protect their software and systems from potential exploitation by malicious attackers.

Keep up to date with the latest news and developments regarding CVEs and security vulnerabilities by visiting the National Vulnerability Database at NVD and following trusted security sources such as Mitre's CVE website.

Timeline

Published on: 02/16/2022 01:15:00 UTC
Last modified on: 06/14/2022 11:15:00 UTC