NVD / CVE Program· CNA apache

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

CriticalCVSS 9.8 · v3.1—Proof of concept Fix available

Noroxi assessment

Priority: This week (action score 67/100)

A ready-made attack module is public (Nuclei); exploiting it takes no special expertise.
Public proof-of-concept code exists (GitHub); there is no record of exploitation in the wild.
Probability of exploitation in the next 30 days: 93% (FIRST EPSS); higher than 99.8% of all records.
Anyone who can reach it over the internet can trigger it. No account or password is required. No user action is required. No special conditions are required; it is repeatable.
Fixed version: Apache Software Foundation Apache Solr 8.8.2.
Mentioned 2 times in Turkish national cyber security advisories (siberguvenlik.gov.tr).

Don’t wait for the next maintenance window. Upgrade to Apache Software Foundation Apache Solr 8.8.2 or later.

Generated automatically from the record's data: CVSS (NVD and CNA), CISA KEV and SSVC, FIRST EPSS, exploit sources, fixed versions. How we calculate it

Primary sources: NVD · CVE.org · FIRST EPSS

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.

GHSA-5phw-3jrp-3vj8

Published: Apr 13, 2021
Updated: Jun 16, 2026
EPSS: 93.0% · 99th percentile
CWE: CWE-918

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Action score

This week

Don’t wait for the next maintenance window.

CVSS: 39 / 40 · 9.8 / 10
CISA KEV: 0 / 30 · Not listed
EPSS: 28 / 30 · 93.0%

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Not in KEV: no record of exploitation in the wild
Proof of concept exists, no weaponized module
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Noroxi analysis

What does it mean in your environment?

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Affected systems

Is your version affected?

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Vendor	Product	CPE
apache	solr	cpe:2.3:a:apache:solr

Versions reported by the vendor

Affected version ranges reported by the assigning authority (apache). Independent of NVD's CPE analysis and usually ahead of it.

Apache Software Foundation Apache Solr
- Apache Solr and later · before 8.8.2affected

Affected versions

NVD version ranges (for catalog products). Add the product to your stack with a version and matching uses these.

apache solrbefore 8.8.2

Package-level exposure

OSV and GitHub Advisory data: ecosystem, package and range. SBOM matching uses this table.

Ecosystem	Package	Affected range	Fix
Debian:12	lucene-solr	before 3.6.2+dfsg-23	3.6.2+dfsg-23
Maven	org.apache.solr:solr-parent	before 8.8.2	8.8.2

Same product

apache: all records

Other highest-scoring records for the same primary product.

CVE-2019-17558Apache Solr 5.0.0 to Apache Solr 8.3.1 are vulnerable to a Remote Code Execution through the VelocityResponseWriter.KEV
90Now
CVE-2019-0193In Apache Solr, the DataImportHandler, an optional but popular module to pull in data from databases and other sources, has a feature in…KEV
83Now
CVE-2024-45216Apache Solr: Authentication bypass possible using a fake URL Path ending
67This week

Published before and after this one in the same product

← EarlierCVE-2020-13941Aug 17, 2020 · Reported in SOLR-14515 (private) and fixed in SOLR-14561 (public), released in Solr version 8.6.0.
37Monitor
← EarlierCVE-2020-13957Oct 13, 2020 · Apache Solr versions 6.6.0 to 6.6.6, 7.0.0 to 7.7.3 and 8.0.0 to 8.6.2 prevents some features considered dangerous (which could be used for…
63This week
Later →CVE-2021-29262Apr 13, 2021 · Misapplied Zookeeper ACLs can result in leakage of configured authentication and authorization settings
32Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / package	Fixed version	Source
Apache Software Foundation Apache Solr	8.8.2 · description	Vendor (CNA)
debian:lucene-solr	3.6.2+dfsg-23 · Debian:12	Package registry (OSV)
Maven:org.apache.solr:solr-parent	8.8.2	Package registry (OSV)

Exploit status

Proof of concept available

A public proof of concept or detection signature exists. Exploit knowledge is out there; don't delay patching.

Evidence

Nuclei detection template ×1
Proof-of-concept repository on GitHub ×5

Noroxi does not host or link to exploit code. Metasploit module names and Nuclei template ids are shown (names, not code); Exploit-DB entries and PoC repositories are given as counts only.

Public exploit evidence
Source	Kind	Date
Proof-of-concept repository on GitHub	5 repositories	2021-04-21 → 2025-10-18
Nuclei detection template	Nuclei template CVE-2021-27905	—

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.