Fixes a bug in Zend Framework's Stream HTTP Wrapper

Exploitation

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

CVSS

9.8 · CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

EPSS

• CVE-2021-21426: 1.20% estimated exploitation activity in the next 30 days; percentile 68.28 (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 CVE-2021-3007: Backport of ZendHttpResponseStream, added certain type checking as a way to prevent exploitation. https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2021-3007 This vulnerability is caused by the unsecured deserialization of an object. In versions higher than Zend Framework 3.0.0, the attacker abuses the Zend3 feature that loads classes from objects in order to upload and execute malicious code in the server. The code can be uploaded using the “callback” parameter, which in this case inserts a malicious code instead of the “callbackOptions” array. Patches Has the problem been patched? What versions should users upgrade to? v20.0.9 v19.4.13

Published by the source

22 Apr 2021, 16:10 UTC

Last modified by the source

1 Feb 2023, 05:05 UTC

Source last checked

26 Oct 2026, 14:01 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-m496-x567-f98c

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# Patch Next advisory brief: CVE-2021-21426

Advisory: Fixes a bug in Zend Framework's Stream HTTP Wrapper
IDs: CVE-2021-21426, GHSA-m496-x567-f98c
Record: https://patchnext.com/advisories/cve-2021-21426 (revision 1, source checked 26 Oct 2026, 14:01 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: Critical (CVSS 9.8)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: openmage/magento-lts 20.0.9, 19.4.13. A vendor fix does not mean a deployment is fixed.

## Affected components
- Packagist openmage/magento-lts: affected <= 19.4.12; >= 20.0.0, <= 20.0.8; fixed in 19.4.13, 20.0.9

## Suggested inspection (read-only)
- Packagist openmage/magento-lts: 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 openmage/magento-lts.
- 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-m496-x567-f98c (GitHub-reviewed advisory GHSA-m496-x567-f98c lists affected ranges: Packagist openmage/magento-lts >=0 =20.0.0 <=20.0.8)

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