CVE-2019-18887: Symfony/http kernel Symfony Http-Kernel Has Non-constant Time Vulnerability

HIGH
Advisory Identifier: GHSA-q8hg-pf8v-cxrv
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CVSS 8.1
CWE-203
Published
Advisory Summary

CVE-2019-18887 is a HIGH (CVSS 8.1) symfony http-kernel has non-constant time vulnerability (CWE-203: Observable Discrepancy) affecting Symfony/http kernel libraries in the Packagist ecosystem. The issue involves symfony http-kernel has non-constant time comparison in urisigner. Remediation is available by upgrading affected packages to version 2.8.52, 3.4.35, 4.2.12, 4.3.8.

CVE-2019-18887 at a Glance

CVE Identifier CVE-2019-18887
GHSA Identifier GHSA-q8hg-pf8v-cxrv
Severity HIGH
CVSS v3.1 Base Score 8.1
CWE Classification CWE-203: Observable Discrepancy
Affected Product Symfony/http kernel
Package Ecosystem Packagist
Published Date
Last Updated

Security Impact

CVSS: 8.1

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

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

How to Fix CVE-2019-18887

To remediate this vulnerability, upgrade all affected Symfony/http 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.

symfony/http-kernel fixed: 2.8.52 
Upgrade symfony/http-kernel to 2.8.52
symfony/http-kernel fixed: 3.4.35 
Upgrade symfony/http-kernel to 3.4.35
symfony/http-kernel fixed: 4.2.12 
Upgrade symfony/http-kernel to 4.2.12
symfony/http-kernel fixed: 4.3.8 
Upgrade symfony/http-kernel to 4.3.8
symfony/symfony fixed: 2.8.52 
Upgrade symfony/symfony to 2.8.52
symfony/symfony fixed: 3.4.35 
Upgrade symfony/symfony to 3.4.35
symfony/symfony fixed: 4.2.12 
Upgrade symfony/symfony to 4.2.12
symfony/symfony fixed: 4.3.8 
Upgrade symfony/symfony to 4.3.8
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 symfony/http-kernel

How to Check if You Are Affected

To determine whether your application is affected by CVE-2019-18887, inspect your project dependencies for Symfony/http kernel:

inspect dependencies for symfony/http-kernel

Analyze the terminal output to locate any version of Symfony/http kernel in your dependency tree. If any resolved version matches the vulnerable ranges listed in the table below (for example, versions earlier than 2.8.52), 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 Symfony/http 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

When checking the signature of an URI (an ESI fragment URL for instance), the URISigner did not used a constant time string comparison function, resulting in a potential remote timing attack vulnerability.

CVE-2019-18887 Affected Symfony/http kernel Versions

8 component(s)
Fixed Versions:
2.8.523.4.354.2.124.3.8
Product / Package Ecosystem Affected Versions Fixed Version
symfony/http-kernel
 Packagist
≥ 2.2.0
< 2.8.52
2.8.52
symfony/http-kernel
 Packagist
≥ 3.0.0
< 3.4.35
3.4.35
symfony/http-kernel
 Packagist
≥ 4.0.0
< 4.2.12
4.2.12
symfony/http-kernel
 Packagist
≥ 4.3.0
< 4.3.8
4.3.8
symfony/symfony
 Packagist
≥ 2.2.0
< 2.8.52
2.8.52
symfony/symfony
 Packagist
≥ 3.0.0
< 3.4.35
3.4.35
symfony/symfony
 Packagist
≥ 4.0.0
< 4.2.12
4.2.12
symfony/symfony
 Packagist
≥ 4.3.0
< 4.3.8
4.3.8

References

NVD — CVE-2019-18887 NVD
https://nvd.nist.gov/vuln/detail/CVE-2019-18887
Symfony/http kernel Source Repository REPOSITORY
https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/http-kernel/CVE-2019-18887.yaml
Symfony/http kernel Source Repository REPOSITORY
https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2019-18887.yaml
Symfony/http kernel Release RELEASE
https://github.com/symfony/symfony/releases/tag/v4.3.8
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DZNXRVHDQBNZQUCNRVZICPPBFRAUWUJX
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UED22BOXTL2SSFMGYKA64ZFHGLLJG3EA
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/VXEAOEANNIVYANTMOJ42NKSU6BGNBULZ
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DZNXRVHDQBNZQUCNRVZICPPBFRAUWUJX
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UED22BOXTL2SSFMGYKA64ZFHGLLJG3EA
lists.fedoraproject.org/archives/list/packa... WEB
https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VXEAOEANNIVYANTMOJ42NKSU6BGNBULZ
symfony.com/blog/cve-2019-18887... WEB
https://symfony.com/blog/cve-2019-18887-use-constant-time-comparison-in-urisigner
symfony.com/blog/symfony-4-3-8-... WEB
https://symfony.com/blog/symfony-4-3-8-released
symfony.com/cve-2019-18887 WEB
https://symfony.com/cve-2019-18887

Frequently Asked Questions

What is CVE-2019-18887?
CVE-2019-18887 is a security vulnerability in Symfony/http kernel involving Symfony Http-Kernel has non-constant time comparison in UriSigner under CWE-203: Observable Discrepancy.
Which Symfony/http kernel versions are affected?
Affected versions include releases prior to 2.8.52, 3.4.35, 4.2.12, 4.3.8 across affected packages: symfony/http-kernel, symfony/symfony.
What version fixes CVE-2019-18887?
Upgrading to 2.8.52, 3.4.35, 4.2.12, 4.3.8 (or the latest patched release for your respective branch) resolves the vulnerability.
Is symfony/http-kernel affected?
Yes, symfony/http-kernel is affected in releases prior to 2.8.52, 3.4.35, 4.2.12, 4.3.8. Upgrade your dependency to 2.8.52, 3.4.35, 4.2.12, 4.3.8 or later.
Is symfony/symfony affected?
Yes, symfony/symfony is affected in releases prior to 2.8.52, 3.4.35, 4.2.12, 4.3.8. Upgrade your dependency to 2.8.52, 3.4.35, 4.2.12, 4.3.8 or later.
What is the CVSS score of CVE-2019-18887?
CVE-2019-18887 has a CVSS v3.1 base score of 8.1 (HIGH) with vector string CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H.
What CWE is associated with CVE-2019-18887?
CVE-2019-18887 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-2019-18887?
Run the dependency tree command: 'inspect dependencies for symfony/http-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-q8hg-pf8v-cxrv",
  "modified" : "2024-02-01T15:49:08Z",
  "published" : "2022-03-26T00:22:49Z",
  "aliases" : [ "CVE-2019-18887" ],
  "summary" : "Symfony Http-Kernel has non-constant time comparison in UriSigner",
  "details" : "When checking the signature of an URI (an ESI fragment URL for instance), the URISigner did not used a constant time string comparison function, resulting in a potential remote timing attack vulnerability.",
  "severity" : [ {
    "type" : "CVSS_V3",
    "score" : "CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H"
  } ],
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    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
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      }, {
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    } ]
  }, {
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    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
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    } ]
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    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.0.0"
      }, {
        "fixed" : "4.2.12"
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    } ]
  }, {
    "package" : {
      "ecosystem" : "Packagist",
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    "ranges" : [ {
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    "ranges" : [ {
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        "introduced" : "3.0.0"
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        "fixed" : "3.4.35"
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    } ]
  }, {
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      "ecosystem" : "Packagist",
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    } ]
  }, {
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      "name" : "symfony/symfony"
    },
    "ranges" : [ {
      "type" : "ECOSYSTEM",
      "events" : [ {
        "introduced" : "4.3.0"
      }, {
        "fixed" : "4.3.8"
      } ]
    } ]
  } ],
  "references" : [ {
    "type" : "ADVISORY",
    "url" : "https://nvd.nist.gov/vuln/detail/CVE-2019-18887"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/http-kernel/CVE-2019-18887.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/FriendsOfPHP/security-advisories/blob/master/symfony/symfony/CVE-2019-18887.yaml"
  }, {
    "type" : "WEB",
    "url" : "https://github.com/symfony/symfony/releases/tag/v4.3.8"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/DZNXRVHDQBNZQUCNRVZICPPBFRAUWUJX"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/UED22BOXTL2SSFMGYKA64ZFHGLLJG3EA"
  }, {
    "type" : "WEB",
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  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/DZNXRVHDQBNZQUCNRVZICPPBFRAUWUJX"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/UED22BOXTL2SSFMGYKA64ZFHGLLJG3EA"
  }, {
    "type" : "WEB",
    "url" : "https://lists.fedoraproject.org/archives/list/package-announce@lists.fedoraproject.org/message/VXEAOEANNIVYANTMOJ42NKSU6BGNBULZ"
  }, {
    "type" : "WEB",
    "url" : "https://symfony.com/blog/cve-2019-18887-use-constant-time-comparison-in-urisigner"
  }, {
    "type" : "WEB",
    "url" : "https://symfony.com/blog/symfony-4-3-8-released"
  }, {
    "type" : "WEB",
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  } ],
  "database_specific" : {
    "cwe_ids" : [ "CWE-203" ],
    "severity" : "HIGH",
    "github_reviewed" : true,
    "github_reviewed_at" : "2022-03-26T00:22:49Z",
    "nvd_published_at" : "2019-11-21T23:15:13Z"
  }
}