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HIGH severity

Server-Side Request Forgery in Apache SolrGHSA-5phw-3jrp-3vj8

HIGH

GHSA-5phw-3jrp-3vj8 is a high-severity (CVSS 7.1) Server-Side Request Forgery (SSRF) vulnerability in org.apache.solr:solr-parent. 7 public exploit references exist, so weaponization risk is real. A fix is available for org.apache.solr:solr-parent — see the affected versions and patch details below.

Also known asBIT-solr-2021-27905CVE-2021-27905
Published
Updated
Affected
1 pkg
Patched
1 / 1
Exploits
7 known
Exploitation data as of Oct 23, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
93.1%probability of exploitation in next 30 days
Very High Risk0.00%
Lower risk than most CVEs100th percentile — riskier than 100% of all scored CVEsHighest risk
92.6%93.2%93.8%94.4%93.9%93.1%Apr 26Jul 26Oct 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

GHSA-5phw-3jrp-3vj8 by exploitation likelihood (EPSS) against impact (CVSS). In the shaded patch-first corner (EPSS 50%+, CVSS 7.0+).

Where this sits among everything scored

Of 395,249 CVEs with a current EPSS score, this one falls in the ≥ 90% band (highlighted). Counts from FIRST.org, log-scaled.

Real-World Exposure

1 pkg affected
☕org.apache.solr:solr-parent

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.

Description

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.

Affected Packages

1 total 1 fixed
EcosystemPackageVulnerable rangeFix
☕Mavenorg.apache.solr:solr-parentall versions8.8.2org.apache.solr:solr-parent:8.8.2

Affected Products

1 product · 1 configurations
Application
solrapache
< 8.8.2
range
Exploits & PoCs
7

Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.

The ReplicationHandler (normally registered at "/replication" under a So…

github.comGithubApr 2021

The ReplicationHandler (normally registered at "/replication" under a So…

github.comGithubAug 2021

The ReplicationHandler (normally registered at "/replication" under a So…

github.comGithubNov 2022

The ReplicationHandler (normally registered at "/replication" under a So…

unit42.paloaltonetworks.comAPIApr 2021

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.apache.solr:solr-parent, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    Update org.apache.solr:solr-parent to 8.8.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-5phw-3jrp-3vj8 is resolved across your whole dependency graph.

  3. Workarounds

    Restrict outbound requests from the affected component to an allowlist of hosts, block access to link-local and internal address ranges at the network layer, and require authentication on internal services so a forged request cannot reach them unauthenticated.

How to detect GHSA-5phw-3jrp-3vj8

A community-maintained Nuclei template exists for this CVE. You can scan for it directly:

nuclei -id ghsa-5phw-3jrp-3vj8 -u https://target
Template
Apache Solr <=8.8.1 - Server-Side Request Forgery
Severity
critical
Impact
Successful exploitation of this vulnerability can lead to unauthorized access to internal resources, data leakage, and potential remote code execution.
Remediation
This issue is resolved in Apache Solr 8.8.2 and later.

Template by ProjectDiscovery nuclei-templates (hackergautam), MIT licensed. View the full template. Scan only systems you are authorised to test.

Fixing This On Your OS

If you run this on a Linux distribution, patch through your package manager against the distro's own security advisory below — it tracks the exact backported fix for your release, which can ship on a different timeline (and sometimes a different severity) than the upstream project.

Red HatImportant
Workaround published by Red Hat
Restrict access to the replication handler to only internal Solr instances.
Source: Red Hat security advisory for GHSA-5phw-3jrp-3vj8 (CC BY 4.0)

Frequently Asked Questions

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.
O3 Security · Impact-Aware SCA

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Server-Side Request Forgery in Apache Solr (High 7.1)