guzzlehttp/guzzle-services' XML Request Serialization Vulnerable to XML Injection via CDATA Terminator

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

5.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:N/I:L/A:N

EPSS

• CVE-2026-53723: 0.22% estimated exploitation activity in the next 30 days; percentile 12.51 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Impact guzzlehttp/guzzle-services does not safely serialize scalar XML element values containing the CDATA terminator ]]. The XML request serializer writes values containing <, , or & with XMLWriter::writeCData($value). If attacker-controlled input contains ]], the CDATA section closes early and the remainder is interpreted as XML markup. This is an outgoing request-body integrity issue, not a response parsing issue. The attacker does not need to control the service description or schema. Users are affected when all of the following are true: 1. The application uses guzzlehttp/guzzle-services to serialize outgoing requests. 2. A request parameter or additionalParameters schema uses location: xml. 3. The value is serialized as XML element text, not an XML attribute. 4. The value can contain attacker-controlled, user-controlled, tenant-controlled, or otherwise untrusted input. 5. The value is not constrained by a safe enum, pattern, or custom filter that excludes ]]. 6. The downstream…

Published by the source

11 Jun 2026, 13:05 UTC

Last modified by the source

15 Jul 2026, 21:58 UTC

Source last checked

26 Oct 2026, 14:50 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-q8r6-5hfw-5jff

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# Patch Next advisory brief: CVE-2026-53723

Advisory: guzzlehttp/guzzle-services' XML Request Serialization Vulnerable to XML Injection via CDATA Terminator
IDs: CVE-2026-53723, GHSA-q8r6-5hfw-5jff
Record: https://patchnext.com/advisories/cve-2026-53723 (revision 1, source checked 26 Oct 2026, 14:50 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Medium (CVSS 5.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: guzzlehttp/guzzle-services 1.5.4. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist guzzlehttp/guzzle-services: affected < 1.5.4; fixed in 1.5.4

## Suggested inspection (read-only)
- Packagist guzzlehttp/guzzle-services: check the installed version with your package manager.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on guzzlehttp/guzzle-services.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://github.com/advisories/GHSA-q8r6-5hfw-5jff (GitHub-reviewed advisory GHSA-q8r6-5hfw-5jff lists affected ranges: Packagist guzzlehttp/guzzle-services >=0 <1.5.4)

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