CVE-2021-27905

9.8 CRITICAL 93% exploit odds Drop everything Fix listed Disclosure Server

What it is

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.

At a glance

Exploitability: Can be exploited over the network without logging in. High risk of data exposure, data tampering, service disruption.
Exploit odds: 93.1% chance of exploitation in the next 30 days (EPSS). Higher than most.
Fix: A patch, advisory or fixed version is referenced. Upgrade or apply it.

Timeline

2021-03-02 00:00 UTC ReservedThe CVE id was reserved by its CNA
2021-04-13 07:15 UTC PublishedDisclosed publicly on CVE.org and NVD
2026-06-17 03:45 UTC Last updatedMost recent change to the record

Why it ranks here

Exploited in the wild: no, CISA does not list it.
Exploit odds: 93.1% in the next 30 days (EPSS).
Severity: 9.8 CRITICAL (CVSS).
Fix: a patch or advisory is linked.
It meets the bar for Drop everything: critical, and exploited or very likely to be.

Details

Published: 2021-04-13 07:15 UTC
Last modified: 2026-06-17 03:45 UTC
Exploit probability: 93.1% · EPSS, next 30 days
Weakness: CWE-918 · Server-side request forgery
Record status: Modified

Affected

Apache Solr < 8.8.2

Attack profile CVSS 3.1 · 9.8

Attack vector: Network
Complexity: Low
Privileges needed: None
User interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: High

Raw vector

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

Is it in your code?

Hand this to your coding agent. It searches your project for the affected products and checks versions. Nothing leaves your machine.

Read https://cve-list.com/agent/cve/CVE-2021-27905.md and follow it. Check whether this project is affected by CVE-2021-27905. Read only. Don't change anything and don't upload my code. Tell me yes, no or not sure, with the file as proof.

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Fix and advisories

References

NVD record · CVE.org record