CVE-2021-27905: SSRF vulnerability with the Replication handler

Reference page built from the source records below, each shown as its source publishes it. Dataset version ref-e2ea17d04b17, updated 2026-06-17T03:45:35.170Z.

NVD analysis

Status
Modified
Published
2021-04-13T07:15:12.137
Last modified
2026-06-17T03:45:35.170
Weaknesses
CWE-918

The ReplicationHandler (normally registered at "/replication" under a Solr core) in Apache Solr has a "masterUrl" (also "leaderUrl" alias) parameter that is used to designate another ReplicationHandler on another Solr core to replicate index data into the local core. To prevent a SSRF vulnerability, Solr ought to check these parameters against a similar configuration it uses for the "shards" parameter. Prior to this bug getting fixed, it did not. This problem affects essentially all Solr versions prior to it getting fixed in 8.8.2.

MetricScoreSeverityVectorScored by
CVSS 3.19.8CRITICALCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H[email protected] (Primary)
CVSS 2.07.5HIGHAV:N/AC:L/Au:N/C:P/I:P/A:P[email protected] (Primary)

References

This product uses the NVD API but is not endorsed or certified by the NVD.

Read on 2026-11-03T01:43:01.649Z under licence nvd-api-terms-of-use@ff2a5288 from https://services.nvd.nist.gov/rest/json/cves/2.0?cveId=CVE-2021-27905

CVE record

Title (CNA)
SSRF vulnerability with the Replication handler
Assigner
apache
State
PUBLISHED
Published
2021-04-13T06:35:20.000Z
Updated
2024-08-03T21:33:16.792Z
Problem types
CWE-918 Server-Side Request Forgery (SSRF)

The ReplicationHandler (normally registered at "/replication" under a Solr core) in Apache Solr has a "masterUrl" (also "leaderUrl" alias) parameter that is used to designate another ReplicationHandler on another Solr core to replicate index data into the local core. To prevent a SSRF vulnerability, Solr ought to check these parameters against a similar configuration it uses for the "shards" parameter. Prior to this bug getting fixed, it did not. This problem affects essentially all Solr versions prior to it getting fixed in 8.8.2.

References

Read on 2026-11-03T01:07:13.376Z under licence cve-terms-of-use@81bfa2f3 from https://raw.githubusercontent.com/CVEProject/cvelistV5/main/cves/2021/27xxx/CVE-2021-27905.json

Also known as / affected packages

Detection rules (SigmaHQ)

SigmaHQ rules whose own tags name this CVE. Each rule page shows the rule as its author published it.

Defensive techniques (MITRE D3FEND)

D3FEND maps these defensive techniques to the weakness (CWE) that NVD lists for this CVE, through the digital artifacts the weakness affects. D3FEND does not say they stop this vulnerability.

CWE-918: Server-Side Request Forgery (SSRF)

D3FEND ontology version 1.6.0.

Read on 2026-11-03T00:03:22.605Z under licence d3fend-terms-of-use@f98cbc7e from https://d3fend.mitre.org/api/weakness/cwe/CWE-918.json

MITRE D3FEND™ knowledge graph. © 2025 The MITRE Corporation.
"The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use D3FEND for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." Terms: https://d3fend.mitre.org/tou/

Sources and licences

  • National Vulnerability Database (NIST)

    This product uses the NVD API but is not endorsed or certified by the NVD.

    NVD API Terms of Use (NIST publications in the public domain, 17 U.S.C. 105)

  • CVE Program, The MITRE Corporation

    Copyright © 1999-2026, The MITRE Corporation. CVE is a trademark and the CVE logo is a registered trademark of The MITRE Corporation. CVE Usage: MITRE hereby grants you a perpetual, worldwide, non-exclusive, no-charge, royalty-free, irrevocable copyright license to reproduce, prepare derivative works of, publicly display, publicly perform, sublicense, and distribute Common Vulnerabilities and Exposures (CVE™). Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy.

    CVE Program Terms of Use ("CVE Usage" licence)

  • GitHub Advisory Database via OSV.dev

    GHSA-5phw-3jrp-3vj8: GitHub Advisory Database, https://github.com/advisories/GHSA-5phw-3jrp-3vj8. Licensed CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/), provided as is, without warranties. Retrieved via OSV.dev (https://osv.dev/vulnerability/GHSA-5phw-3jrp-3vj8), which enriches records; fields selected and reformatted by ransomware-tracker.com.

    CC BY 4.0

  • SigmaHQ

    "Potential CVE-2021-27905 Exploitation Attempt" by @gott_cyber (SigmaHQ). Rule: https://github.com/SigmaHQ/sigma/blob/ccbb0369507f796db0b0ae6854c8a2be471b9d84/rules-emerging-threats/2021/Exploits/CVE-2021-27905/web_cve_2021_27905_apache_solr_exploit.yml.
    Licensed under the Detection Rule License (DRL) 1.1: https://github.com/SigmaHQ/Detection-Rule-License

    Detection Rule License (DRL) 1.1

  • MITRE D3FEND

    MITRE D3FEND™ knowledge graph. © 2025 The MITRE Corporation.
    "The MITRE Corporation (MITRE) hereby grants you a non-exclusive, royalty-free license to use D3FEND for research, development, and commercial purposes. Any copy you make for such purposes is authorized provided that you reproduce MITRE's copyright designation and this license in any such copy." Terms: https://d3fend.mitre.org/tou/

    MITRE D3FEND Terms of Use (site + knowledge graph); source repo MIT

Cite this page

Dragons Eye Ransomware Tracker, "CVE-2021-27905: SSRF vulnerability with the Replication handler",
entity page, dataset version ref-e2ea17d04b17, updated 2026-06-17T03:45:35.170Z,
https://ransomware-tracker.com/cve/CVE-2021-27905 (accessed 2026-11-03).
Underlying source: National Vulnerability Database (NIST), CVE API 2.0, record last modified 2026-06-17T03:45:35.170.
Underlying source: CVE List (CVE Program, The MITRE Corporation), record updated 2024-08-03T21:33:16.792Z.
Underlying source: GitHub Advisory Database, GHSA-5phw-3jrp-3vj8, via OSV.dev, modified 2024-02-17T05:52:04.882037Z.
Underlying source: SigmaHQ rule 0bbcd74b-0596-41a4-94a0-4e88a76ffdb3, commit ccbb0369507f796db0b0ae6854c8a2be471b9d84.
Underlying source: MITRE D3FEND, ontology version 1.6.0.

Pages change. The dataset version identifies the data, but no archive of old versions is kept, so this citation cannot be replayed later.

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