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CVE-2021-27905

86
FAUCET Score

CVE-2021-27905 is a critical Server-Side Request Forgery (SSRF) vulnerability affecting Apache Solr versions prior to 8.8.2. The vulnerability arises from insufficient validation of the "masterUrl" parameter within the ReplicationHandler, allowing an attacker to force the Solr instance to make requests to arbitrary URLs. This flaw carries a CVSS score of 9.8 (CRITICAL), indicating a network-based attack with low complexity, requiring no user interaction, and leading to complete compromise of confidentiality, integrity, and availability. While not listed in CISA KEV, exploit templates exist for tools like Nuclei, suggesting readily available proof-of-concept code, though there is no evidence of widespread active exploitation or significant community discussion.

Impacted Technologies

VendorProductVersion(s)CPE
< 8.8.2CPE matchmatch criteria
cpe:2.3:a:apache:solr:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.8CRITICAL

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Attack Vector
NETWORK
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
UNCHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
3.9
Impact Score
5.9
CvssVersion
3.1

Exploit Intelligence

EPSS Score
93.05%
Probability of exploitation in next 30 days
EPSS Percentile
99.8%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
Nuclei: CVE-2021-27905 · Apr 23, 2021
This CVE's current EPSS score of 0.9305 is in the 99th percentile among its peer group of 36,862 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.3 Bluesky, 0.3 Mastodon, and 2.4 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (1)

mavenpatch availablevia ghsa
Product: org.apache.solr:solr-parentFixed in: 8.8.2

Vendor Advisories (2)

mavenGHSA-5phw-3jrp-3vj8high

Server-Side Request Forgery in Apache Solr

May 10, 2021
redhatCVE-2021-27905Important

solr: SSRF vulnerability with the Replication handler

Apr 12, 2021

References

lists.apache.org / thread.html/r0ddc3a82bd7523b1453cb7a5e09eb5559517145425074a42eb326b10%40%3Cannounce.apache.org%3E
Mailing ListVendor Advisory
lists.apache.org / thread.html/r140128dc6bb4f4e0b6a39e962c7ca25a8cbc8e48ed766176c931fccc%40%3Cusers.solr.apache.org%3E
lists.apache.org / thread.html/r3da74965aba2b5f5744b7289ad447306eeb2940c872801819faa9314%40%3Cusers.solr.apache.org%3E
lists.apache.org / thread.html/r6ccec7fc54d82591b23c143f1f6a6e38f6e03e75db70870e4cb14a1a%40%3Ccommits.ofbiz.apache.org%3E
lists.apache.org / thread.html/r720a4a0497fc90bad5feec8aa18b777912ee15c7eeb5f882adbf523e%40%3Ccommits.ofbiz.apache.org%3E
lists.apache.org / thread.html/r78a3a4f1138a1608b0c6d4a2ee7647848c1a20b0d5c652cd9b02c25a%40%3Ccommits.ofbiz.apache.org%3E
lists.apache.org / thread.html/r8f1152a43c36d878bbeb5a92f261e9efaf3af313b033d7acfccea59d%40%3Cnotifications.ofbiz.apache.org%3E
lists.apache.org / thread.html/r95df34bb158375948da82b4dfe9a1b5d528572d586584162f8f5aeef%40%3Cusers.solr.apache.org%3E
lists.apache.org / thread.html/rae9ccaecce9859f709ed1458545d90a4c07163070dc98b5e9e59057f%40%3Cnotifications.ofbiz.apache.org%3E
lists.apache.org / thread.html/rd232d77c57a8ce172359ab098df9512d8b37373ab87c444be911b430%40%3Cnotifications.ofbiz.apache.org%3E
lists.apache.org / thread.html/re9d64bb8e5dfefddcbf255adb4559e13a0df5b818da1b9b51329723f%40%3Cnotifications.ofbiz.apache.org%3E
security.netapp.com / advisory/ntap-20210611-0009
Third Party Advisory