CVE-2026-53723: Guzzle Guzzle Services XML injection in request serializer

CVE-2026-53723 · Severity: medium · CVSS 5.8 · Published 2026-06-11

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.

Vendors: Guzzle, Packagist.

Quick answers

Is CVE-2026-53723 exploited in the wild?
No. Junglewise Threat Intelligence has no report of CVE-2026-53723 being exploited in the wild.
How severe is CVE-2026-53723?
Medium severity, with a CVSS score of 5.8, published 11 June 2026.
Which products and versions are affected?
Guzzle Services < 1.5.4; guzzlehttp/guzzle-services (Packagist) < 1.5.4, ECOSYSTEM:introduced=0,fixed=1.5.4.
Is there a fix for CVE-2026-53723?
Yes. guzzlehttp/guzzle-services (Packagist): upgrade to 1.5.4 or later. Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-53723 attacked?
It is attacked over the network, in a software library.
Am I affected by CVE-2026-53723?
Check whether you run Guzzle Services or guzzlehttp/guzzle-services (Packagist) at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

How to fix

  • guzzlehttp/guzzle-services (Packagist): upgrade to 1.5.4 or later
    composer require guzzlehttp/guzzle-services:^1.5.4

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

Identifiers

  • CVE-2026-53723
  • GHSA-q8r6-5hfw-5jff

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

References

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