Executive brief
Guzzle Services is a library used by PHP applications to communicate with web services using structured descriptions. A vulnerability in how it handles XML data allows an attacker to inject malicious commands or data into outgoing requests sent by the application. This could allow an attacker to bypass security boundaries, modify privileged fields, or alter the intended behavior of the downstream service being contacted.
Technical details
Guzzle Services versions prior to 1.5.4 fail to properly sanitize the CDATA terminator (]]>) when serializing scalar XML element values. The XML request serializer uses XMLWriter::writeCData() for values containing special characters; if an attacker provides input containing the terminator, the CDATA section closes prematurely, allowing the remaining input to be interpreted as raw XML markup. This is an outgoing request-body integrity issue (XML Injection) that occurs when 'location: xml' is used in service descriptions. Attackers can exploit this to smuggle privileged fields or alter operation semantics in downstream services. The issue is resolved in version 1.5.4 by splitting embedded CDATA terminators.
Affected products
- Guzzle guzzle-services < 1.5.4
Timeline
- 2026-06-02: advisory: GitHub Security Advisory published
- 2026-06-11: disclosed: CVE published to NVD
- 2026-06-11: patched: Fix released in version 1.5.4