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CVE-2021-27905

SSRF vulnerability with the Replication handler

9.8 CriticalPublic exploitFix available

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.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
High

Exploit likelihood

93.1%Up 92.6 points since Apr 14, 2021
90%50%10%1%

What each source reports

NVD Score used 9.8

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.

Record
CVE-2021-27905
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
CVSS 2.0
7.5 HighAV:N/AC:L/Au:N/C:P/I:P/A:P
Weakness
CWE-918
Updated
2026-11-02
CVE List No score

SSRF vulnerability with the Replication handler

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.

Record
CVE-2021-27905
Weakness
CWE-918
Updated
2026-11-02
EUVDEUVD-2021-0959 No score

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.

Record
EUVD-2021-0959
Updated
2026-11-03
GitHub AdvisoriesGHSA-5phw-3jrp-3vj8 7.1

Server-Side Request Forgery in Apache Solr

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.

Record
GHSA-5phw-3jrp-3vj8
CVSS 3.1
7.1 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N
Weakness
CWE-918
Updated
2026-11-02
OSV 9.8

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.

Record
CVE-2021-27905
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVDEBIAN-CVE-2021-27905 9.8

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.

Record
DEBIAN-CVE-2021-27905
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVGHSA-5phw-3jrp-3vj8 7.1

Server-Side Request Forgery in Apache Solr

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.

Record
GHSA-5phw-3jrp-3vj8
CVSS 3.1
7.1 HighCVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:H/I:L/A:N
Weakness
CWE-918
Updated
2026-11-02
OSVUBUNTU-CVE-2021-27905 9.8

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.

Record
UBUNTU-CVE-2021-27905
CVSS 3.1
9.8 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H
Updated
2026-11-02
OSVBIT-solr-2021-27905 No score

SSRF vulnerability with the Replication handler

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.

Record
BIT-solr-2021-27905
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
org.apache.solr:solr-parent
Maven
 before 8.8.2
8.8.2
solr
Bitnami
 before 8.8.2
8.8.2
lucene-solr
Debian:12
 before 3.6.2+dfsg-23
3.6.2+dfsg-23
lucene-solr
Debian:13
 before 3.6.2+dfsg-23
3.6.2+dfsg-23
lucene-solr
Debian:14
 before 3.6.2+dfsg-23
3.6.2+dfsg-23
org.apache.solr:solr-parent
Maven
 before 8.8.2, plus listed versions
1.3.01.4.01.4.13.1.03.2.0
Show 45 moreShow less
3.3.03.4.03.5.03.6.03.6.13.6.24.0.04.0.0-ALPHA4.0.0-BETA4.1.04.10.04.10.14.10.24.10.34.10.44.2.04.2.14.3.04.3.14.4.04.5.04.5.14.6.04.6.14.7.04.7.14.7.24.8.04.8.14.9.04.9.15.0.05.1.05.2.05.2.15.3.05.3.15.3.25.4.05.4.15.5.05.5.15.5.25.5.35.5.4
8.8.2
lucene-solr
Ubuntu:Pro:14.04:LTS
 All versions, plus listed versions
3.6.2+dfsg-13.6.2+dfsg-23.6.2+dfsg-2ubuntu0.1~esm13.6.2+dfsg-2ubuntu0.1~esm23.6.2+dfsg-2ubuntu0.1~esm4
 None known
lucene-solr
Ubuntu:Pro:16.04:LTS
 All versions, plus listed versions
3.6.2+dfsg-73.6.2+dfsg-83.6.2+dfsg-8ubuntu0.13.6.2+dfsg-8ubuntu0.1+esm1
 None known
lucene-solr
Ubuntu:Pro:18.04:LTS
 All versions, plus listed versions
3.6.2+dfsg-103.6.2+dfsg-113.6.2+dfsg-18~18.043.6.2+dfsg-18~18.04.1~esm2
 None known
lucene-solr
Ubuntu:20.04:LTS
 All versions, plus listed versions
3.6.2+dfsg-203.6.2+dfsg-22
 None known
Show 5 moreShow less
Affected packages
PackageAffectedFixed
lucene-solr
Ubuntu:22.04:LTS
 All versions, plus listed versions
3.6.2+dfsg-24
 None known
lucene-solr
Ubuntu:24.04:LTS
 All versions, plus listed versions
3.6.2+dfsg-26
 None known
lucene-solr
Ubuntu:25.10
 All versions, plus listed versions
3.6.2+dfsg-26
 None known
lucene-solr
Ubuntu:26.10
 All versions, plus listed versions
3.6.2+dfsg-27
 None known
lucene-solr
Ubuntu:26.04:LTS
 All versions, plus listed versions
3.6.2+dfsg-263.6.2+dfsg-27
 None known

Public exploits

Links only. Every CVE stores no exploit code.

Public exploits
SourceLinkDate
NucleiApache Solr <=8.8.1 - Server-Side Request Forgery
PoC in GitHubHenry4E36/Solr-SSRF2021-04-21
PoC in GitHubRIZZZIOM/CVE-2021-279052025-10-18
PoC in GitHubW2Ning/Solr-SSRF2021-04-25
PoC in GitHubmurataydemir/CVE-2021-279052021-08-10
PoC in GitHubpdelteil/CVE-2021-27905.POC2022-11-03

History

History
RecordedChangedSources
aliasesEUVD
first indexedCVE List, GitHub Advisories, Nuclei, NVD, OSV, PoC in GitHub

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2021-27905 is a critical vulnerability (CVSS 9.8) in Apache Solr, published April 13, 2021. Public exploit code exists. EPSS puts the chance of exploitation in the next 30 days at 93.1%, the 99th percentile. Fixed in org.apache.solr:solr-parent 8.8.2.

References

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