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CRITICAL severity

Fixes a bug in Zend Framework's Stream HTTP WrapperGHSA-m496-x567-f98c

CRITICAL

GHSA-m496-x567-f98c is a critical-severity (CVSS 9.8) Deserialization of Untrusted Data vulnerability in openmage/magento-lts. A fix is available for openmage/magento-lts — see the affected versions and patch details below.

Also known asCVE-2021-21426
Published
Updated
Affected
2 pkgs
Patched
2 / 2
Exploits
None indexed
Exploitation data as of Oct 11, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
1.2%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs67th percentile — riskier than 67% of all scored CVEsHighest risk
0.00%0.57%1.14%1.70%0.4%1.2%Apr 26Aug 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-m496-x567-f98c by exploitation likelihood (EPSS) against impact (CVSS). Outside the shaded patch-first corner.

Where this sits among everything scored

Of 385,738 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

2 pkgs affected
🐘openmage/magento-lts🐘openmage/magento-lts

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

Impact

CVE-2021-3007: Backport of Zend_Http_Response_Stream, 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

Affected Packages

2 total 2 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistopenmage/magento-ltsall versions19.4.13composer require openmage/magento-lts:^19.4.13
🐘Packagistopenmage/magento-lts≥ 20.0.0&&< 20.0.920.0.9composer require openmage/magento-lts:^20.0.9

Affected Products

1 product · 2 configurations
Application
magentoopenmage
≥ 20.0.0 && < 20.0.9
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for openmage/magento-lts, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update openmage/magento-lts to 19.4.13 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-m496-x567-f98c is resolved across your whole dependency graph.

  3. Workarounds

    Do not deserialise data from untrusted sources: where the format allows it, restrict deserialisation to an explicit allowlist of expected types, and prefer a data-only format (JSON, Protobuf) over one that can reconstruct arbitrary objects until you can upgrade.

Frequently Asked Questions

### Impact CVE-2021-3007: Backport of Zend_Http_Response_Stream, 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 _Ha
O3 Security · Impact-Aware SCA

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Fixes a bug in Zend Framework's Stream HTTP Wrapper