CVE-2021-46876: Ezsystems/ezpublish kernel /user/sessions Endpoint Allows Detecting Valid Vulnerability

MODERATE
Advisory Identifier: GHSA-gmrf-99gw-vvwj
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CVSS 5.3
CWE-203
Published
Advisory Summary

CVE-2021-46876 is a MODERATE (CVSS 5.3) /user/sessions endpoint allows detecting valid vulnerability (CWE-203: Observable Discrepancy) affecting Ezsystems/ezpublish kernel libraries in the Packagist ecosystem. The issue involves /user/sessions endpoint allows detecting valid accounts. Remediation is available by upgrading affected packages to version 6.13.8.1, 7.5.15.1.

CVE-2021-46876 at a Glance

CVE Identifier CVE-2021-46876
GHSA Identifier GHSA-gmrf-99gw-vvwj
Severity MODERATE
CVSS v3.1 Base Score 5.3
CWE Classification CWE-203: Observable Discrepancy
Affected Product Ezsystems/ezpublish kernel
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 5.3

The security impact metrics below are parsed directly from the CVSS v3.1 vector string (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N).

Attack Vector Network (AV:N)
Attack Complexity Low (AC:L)
Privileges Required None (PR:N)
User Interaction None (UI:N)
Scope Unchanged (S:U)
Confidentiality Low (C:L)
Integrity None (I:N)
Availability None (A:N)

How to Fix CVE-2021-46876

To remediate this vulnerability, upgrade all affected Ezsystems/ezpublish kernel dependencies to a patched release. Both direct and transitive dependencies should be checked, as frameworks or security libraries may pull in vulnerable versions transitively.

ezsystems/ezpublish-kernel fixed: 6.13.8.1 
Upgrade ezsystems/ezpublish-kernel to 6.13.8.1
ezsystems/ezpublish-kernel fixed: 7.5.15.1 
Upgrade ezsystems/ezpublish-kernel to 7.5.15.1
Verify Direct and Transitive Dependencies

Run the following command in your project directory to verify that all resolved dependencies use the patched release: 

inspect dependencies for ezsystems/ezpublish-kernel

How to Check if You Are Affected

To determine whether your application is affected by CVE-2021-46876, inspect your project dependencies for Ezsystems/ezpublish kernel:

inspect dependencies for ezsystems/ezpublish-kernel

Analyze the terminal output to locate any version of Ezsystems/ezpublish kernel in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 6.13.8.1), your application is affected.

Note: Verify declared build manifests and deployed runtime container environments.

Technical Details

Vulnerability Mechanism & Technical Analysis

This vulnerability is classified under CWE-203: Observable Discrepancy, where the product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor. In Ezsystems/ezpublish kernel, software state validation or input boundaries are circumvented during processing. Review the official source advisory statement below for specific affected components, classes, and reproduction details.

Source Advisory Statement

This Security Advisory is about a vulnerability in eZ Platform v1.13, v2.5, and v3.2, and in Ibexa DXP and Ibexa Open Source v3.3. The /user/sessions endpoint can let an attacker detect if a given username or email refers to a valid account. This can be detected through differences in the response data or response time of certain requests. The fix ensures neither attack is possible. The fix is distributed via Composer. If you come across a security issue in our products, here is how you can report it to us: https://doc.ibexa.co/en/latest/guide/reporting_issues/#toc

CVE-2021-46876 Affected Ezsystems/ezpublish kernel Versions

2 component(s)
Fixed Versions:
6.13.8.17.5.15.1
Product / Package Ecosystem Affected Versions Fixed Version
ezsystems/ezpublish-kernel
 Packagist
≥ 6.13.0
< 6.13.8.1
6.13.8.1
ezsystems/ezpublish-kernel
 Packagist
≥ 7.5.0
< 7.5.15.1
7.5.15.1

References

GitHub Advisory / Wiki ADVISORY
https://github.com/ezsystems/ezpublish-kernel/security/advisories/GHSA-gmrf-99gw-vvwj
NVD — CVE-2021-46876 NVD
https://nvd.nist.gov/vuln/detail/CVE-2021-46876
Security Fix Commit FIX COMMIT
https://github.com/ezsystems/ezpublish-kernel/commit/b496f073c3f03707d3531a6941dc098b84e3cbed
Ezsystems/ezpublish kernel Source Repository REPOSITORY
https://github.com/ezsystems/ezpublish-kernel
packagist.org/packages/ezsystems/... WEB
https://packagist.org/packages/ezsystems/ezpublish-kernel

Frequently Asked Questions

What is CVE-2021-46876?
CVE-2021-46876 is a security vulnerability in Ezsystems/ezpublish kernel involving /user/sessions endpoint allows detecting valid accounts under CWE-203: Observable Discrepancy.
Which Ezsystems/ezpublish kernel versions are affected?
Affected versions include releases prior to 6.13.8.1, 7.5.15.1 across affected packages: ezsystems/ezpublish-kernel.
What version fixes CVE-2021-46876?
Upgrading to 6.13.8.1, 7.5.15.1 (or the latest patched release for your respective branch) resolves the vulnerability.
Is ezsystems/ezpublish-kernel affected?
Yes, ezsystems/ezpublish-kernel is affected in releases prior to 6.13.8.1, 7.5.15.1. Upgrade your dependency to 6.13.8.1, 7.5.15.1 or later.
What is the CVSS score of CVE-2021-46876?
CVE-2021-46876 has a CVSS v3.1 base score of 5.3 (MODERATE) with vector string CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N.
What CWE is associated with CVE-2021-46876?
CVE-2021-46876 is classified under CWE-203: Observable Discrepancy (The product behaves differently or sends different responses under different circumstances in a way that is observable to an unauthorized actor.).
How can I check Packagist dependencies for CVE-2021-46876?
Run the dependency tree command: 'inspect dependencies for ezsystems/ezpublish-kernel'. This command lists direct and transitive dependencies in your build configuration so you can verify if a vulnerable version is resolved.
Machine-readable OSV JSON OSV v1.5 Schema
Normalized schema output
View Raw JSON 
{
  "schema_version" : "1.4.0",
  "id" : "GHSA-gmrf-99gw-vvwj",
  "modified" : "2026-02-03T17:38:56Z",
  "published" : "2021-03-11T17:42:08Z",
  "aliases" : [ "CVE-2021-46876" ],
  "summary" : "/user/sessions endpoint allows detecting valid accounts",
  "details" : "This Security Advisory is about a vulnerability in eZ Platform v1.13, v2.5, and v3.2, and in Ibexa DXP and Ibexa Open Source v3.3. The /user/sessions endpoint can let an attacker detect if a given username or email refers to a valid account. This can be detected through differences in the response data or response time of certain requests. The fix ensures neither attack is possible. The fix is distributed via Composer.\n\nIf you come across a security issue in our products, here is how you can report it to us: https://doc.ibexa.co/en/latest/guide/reporting_issues/#toc",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:N"
  } ],
  "affected" : [ {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "ezsystems/ezpublish-kernel"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "6.13.0"
      }, {
        "fixed" : "6.13.8.1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 6.13.8.0"
    }
  }, {
    "package" : {
      "ecosystem" : "Packagist",
      "name" : "ezsystems/ezpublish-kernel"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "7.5.0"
      }, {
        "fixed" : "7.5.15.1"
      } ]
    } ],
    "database_specific" : {
      "last_known_affected_version_range" : "<= 7.5.15.0"
    }
  } ],
  "references" : [ {
    "type" : "WEB",
    "url" : "https://github.com/ezsystems/ezpublish-kernel/security/advisories/GHSA-gmrf-99gw-vvwj"
  }, {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2021-46876"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/ezsystems/ezpublish-kernel/commit/b496f073c3f03707d3531a6941dc098b84e3cbed"
  }, {
    "type" : "PACKAGE",
    "url" : "https://github.com/ezsystems/ezpublish-kernel"
  }, {
    "type" : "WEB",
    "url" : "https://packagist.org/packages/ezsystems/ezpublish-kernel"
  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-203" ],
    "severity" : "MODERATE",
    "github_reviewed" : true,
    "github_reviewed_at" : "2021-03-11T17:41:49Z",
    "nvd_published_at" : null
  }
}