CVE-2021-27905

CRITICALNVD 9.89.8—
EchelonGraph scoreMEDIUM confidence

This critical-severity CVE scores 9.8 under NVD CVSS v3. EPSS exploit probability: 93.1%, top 0% of all CVEs by exploit prediction. GitHub Security Advisory data not yet ingested — confidence will rise once GHSA publishes (typical lag: hours to days for open-source ecosystem CVEs; never for infrastructure-only CVEs).

Triggered by: NVD CVSS baseline
Sources: epss, nvd
Trending — 3 sources updated this weekElevated
9.8
EchelonGraph verdictPatch this weekExploitation is likely or a public exploit exists.
  • High exploitation likelihood — EPSS 93%
CISA-KEV: Not listedEPSS: 93%CVSS: 9.8Exploit: NoneExposed: 0

No vendor fix yet — apply a workaround or compensating control (WAF / firewall / segmentation) and watch for a patch.

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.

CVSS v3
9.8
EG Score
9.8(medium)
EG Risk
86(Track*)
EG Risk 86/100SSVC: Track*

EG Risk is EchelonGraph's 0–100 priority score: it fuses intrinsic severity with real-world exploitation and automatability so you can rank equal-severity CVEs and fix the most dangerous first. Higher = act sooner. Distinct from the 0–10 EG Score (severity).

How it’s computed
Severity98% × 45%
Exploitation93% × 40%
Automatability30% × 15%
Action: Watch closely — could escalate to Attend.
EPSS
99.8%
KEV
Not listed

Published

April 13, 2021

Last Modified

November 21, 2024

Advisory Details (10)

Auto-updated Jun 10, 2026
No patch confirmed yet.
generic
https://lists.apache.org/thread.html/rd232d77c57a8ce172359ab098df9512d8b37373ab87c444be911b430%40%3Cnotifications.ofbiz.apache.org%3E
generic
https://lists.apache.org/thread.html/rae9ccaecce9859f709ed1458545d90a4c07163070dc98b5e9e59057f%40%3Cnotifications.ofbiz.apache.org%3E
generic
https://lists.apache.org/thread.html/r95df34bb158375948da82b4dfe9a1b5d528572d586584162f8f5aeef%40%3Cusers.solr.apache.org%3E
generic
https://lists.apache.org/thread.html/r8f1152a43c36d878bbeb5a92f261e9efaf3af313b033d7acfccea59d%40%3Cnotifications.ofbiz.apache.org%3E
generic
https://lists.apache.org/thread.html/r78a3a4f1138a1608b0c6d4a2ee7647848c1a20b0d5c652cd9b02c25a%40%3Ccommits.ofbiz.apache.org%3E
generic
https://lists.apache.org/thread.html/r720a4a0497fc90bad5feec8aa18b777912ee15c7eeb5f882adbf523e%40%3Ccommits.ofbiz.apache.org%3E
generic
https://lists.apache.org/thread.html/r6ccec7fc54d82591b23c143f1f6a6e38f6e03e75db70870e4cb14a1a%40%3Ccommits.ofbiz.apache.org%3E
generic
https://lists.apache.org/thread.html/r3da74965aba2b5f5744b7289ad447306eeb2940c872801819faa9314%40%3Cusers.solr.apache.org%3E
generic
https://lists.apache.org/thread.html/r140128dc6bb4f4e0b6a39e962c7ca25a8cbc8e48ed766176c931fccc%40%3Cusers.solr.apache.org%3E
generic
https://lists.apache.org/thread.html/r0ddc3a82bd7523b1453cb7a5e09eb5559517145425074a42eb326b10%40%3Cannounce.apache.org%3E

Affected Packages

(1 across 1 ecosystem)
Maven(1)
PackageVulnerable rangeFixed inDependents
org.apache.solr:solr-parent1.3.0 ... 8.8.1 (101 versions)8.8.2—

Weakness Classification(1)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Data Freshness Timeline

(refreshed 5× in last 7d / 16× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

  1. 2026-07-23 01:59 UTCEG score recompute
  2. 2026-07-22 22:46 UTCEG score recompute
  3. 2026-07-22 14:06 UTCEPSS rescore
  4. 2026-07-22 14:06 UTCEPSS rescore
  5. 2026-07-18 22:59 UTCOSV refresh
  6. 2026-07-15 16:55 UTCEPSS rescore
  7. 2026-07-15 16:55 UTCEPSS rescore
  8. 2026-07-08 15:12 UTCEPSS rescore
  9. 2026-07-06 02:21 UTCEPSS rescore
  10. 2026-07-06 02:21 UTCEPSS rescore
  11. 2026-07-05 02:28 UTCEPSS rescore
  12. 2026-07-01 05:48 UTCOSV refresh
  13. 2026-06-25 13:48 UTCEPSS rescore
  14. 2026-06-25 13:48 UTCEPSS rescore
  15. 2026-06-23 21:31 UTCEPSS rescore
  16. 2026-06-23 21:31 UTCEPSS rescore
  17. 2026-06-21 01:58 UTCEPSS rescore
  18. 2026-06-21 01:58 UTCEPSS rescore
  19. 2026-06-17 17:51 UTCEPSS rescore
  20. 2026-06-15 17:46 UTCEPSS rescore
  21. 2026-06-13 22:58 UTCEPSS rescore
  22. 2026-06-13 22:58 UTCEPSS rescore
  23. 2026-06-13 09:13 UTCOSV refresh
  24. 2026-06-10 22:16 UTCEPSS rescore
  25. 2026-06-10 13:20 UTCEPSS rescore
Show 12 more
  1. 2026-06-06 13:46 UTCEPSS rescore
  2. 2026-06-06 13:46 UTCEPSS rescore
  3. 2026-06-06 13:46 UTCEPSS rescore
  4. 2026-06-05 06:09 UTCEPSS rescore
  5. 2026-06-05 06:09 UTCEPSS rescore
  6. 2026-05-31 22:29 UTCEPSS rescore
  7. 2026-05-31 22:29 UTCEPSS rescore
  8. 2026-05-29 13:42 UTCEPSS rescore
  9. 2026-05-26 18:28 UTCEG score recompute
  10. 2026-05-26 13:42 UTCEPSS rescore
  11. 2026-05-26 07:17 UTCEPSS rescore
  12. 2026-05-26 07:17 UTCEPSS rescore

Publicly available exploits

(5 references)

Working exploit code is in the public domain (4 GitHub PoCs). Defenders should treat patch urgency accordingly — public PoCs typically lead to mass-exploitation within 24-72 hours.

  • GitHub PoCRIZZZIOM/CVE-2021-27905
    First seen Oct 18, 2025

    Apache Solr < 8.8.2 Server Side Request Forgery

    Open source ↗
  • GitHub PoCpdelteil/CVE-2021-27905.POC
    First seen Nov 3, 2022

    POC for LFI related to CVE-2021-27905

    Open source ↗
  • GitHub PoCmurataydemir/CVE-2021-27905
    First seen Aug 10, 2021

    [CVE-2021-27905] Apache Solr ReplicationHandler Server Side Request Forgery (SSRF)

    Open source ↗
  • GitHub PoCHenry4E36/Solr-SSRF
    First seen Apr 21, 2021

    Apache Solr SSRF(CVE-2021-27905)

    Open source ↗
  • Nucleihttp/cves/2021/CVE-2021-27905.yaml
    First seen Jan 1, 2021

    Apache Solr <=8.8.1 - Server-Side Request Forgery

    Open source ↗

Related CVEs(same CWE)

Frequently asked(5)

What is CVE-2021-27905?
CVE-2021-27905 is a critical vulnerability published on April 13, 2021. 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…
When was CVE-2021-27905 disclosed?
CVE-2021-27905 was first published in the National Vulnerability Database on April 13, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-27905 actively exploited?
CVE-2021-27905 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 99.8% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-27905?
CVE-2021-27905 has a CVSS v3 base score of 9.8 (NVD).
How do I remediate CVE-2021-27905?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-27905, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

Dependency Blast Radius

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