VulnerabilityPublished 21 Jan 2026

CVE-2026-22444: Apache Solr · Improper Input Validation

Affects Apache SolrSource CVE Database V5

Not known to be exploited · CVSS 7.1 High.

Data as of 26 Oct 2026, 09:16 UTC

CVSS 3.1 base score

7.1High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.6% chance of exploitation in 30 days – higher than 52% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: Low
Privileges Required: Low
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: Low
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 21 Jan 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Apache Software FoundationApache Solr	Affected >=8.6 <=9.10.0	Fixed in–
Mavenorg.apache.solr/solr-core`pkg:maven/org.apache.solr/solr-core`Other threats	Affected =8.6 <=9.10.0	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should immediately verify if their Apache Solr deployments are running versions 8.6 through 9.10.0 and assess whether the 'create core' API is exposed to untrusted users. They must enable and properly configure the RuleBasedAuthorizationPlugin to restrict 'core-admin-edit' or equivalent permissions exclusively to trusted administrative roles, preventing unauthorized core creation. Upgrading to Apache Solr version 9.10.1 or later is critical to apply the official fix. Additionally, organizations should audit their 'allowPaths' settings to ensure they are correctly restricting filesystem access and review network exposure of Solr APIs, ideally limiting access via firewall rules or VPNs. On Windows systems, disabling UNC path support where not required or applying additional network segmentation can reduce the risk of NTLM hash exposure. Regular monitoring and logging of Solr API usage should be implemented to detect anomalous core creation attempts. Finally, organizations should conduct penetration testing and vulnerability scanning focused on Solr instances to confirm the absence of this vulnerability post-mitigation.

Description

The "create core" API of Apache Solr 8.6 through 9.10.0 lacks sufficient input validation on some API parameters, which can cause Solr to check the existence of and attempt to read file-system paths that should be disallowed by Solr's "allowPaths" security setting https://https://solr.apache.org/guide/solr/latest/configuration-guide/configuring-solr-xml.html#the-solr-element . These read-only accesses can allow users to create cores using unexpected configsets if any are accessible via the filesystem. On Windows systems configured to allow UNC paths this can additionally cause disclosure of NTLM "user" hashes. Solr deployments are subject to this vulnerability if they meet the following criteria: * Solr is running in its "standalone" mode. * Solr's "allowPath" setting is being used to restrict file access to certain directories. * Solr's "create core" API is exposed and accessible to untrusted users. This can happen if Solr's RuleBasedAuthorizationPlugin https://solr.apache.org/guide/solr/latest/deployment-guide/rule-based-authorization-plugin.html is disabled, or if it is enabled but the "core-admin-edit" predefined permission (or an equivalent custom permission) is given to low-trust (i.e. non-admin) user roles. Users can mitigate this by enabling Solr's RuleBasedAuthorizationPlugin (if disabled) and configuring a permission-list that prevents untrusted users from creating new Solr cores. Users should also upgrade to Apache Solr 9.10.1 or greater, which contain fixes for this issue.

Impact

For European organizations, this vulnerability poses significant risks including unauthorized access to sensitive filesystem data and potential exposure of NTLM hashes on Windows-based Solr deployments. This can lead to data confidentiality breaches, unauthorized configuration changes, and facilitate lateral movement within corporate networks. Organizations relying on Solr for search and indexing services, especially those exposing the 'create core' API without strict access controls, may face operational disruptions and increased risk of compromise. The exposure of NTLM hashes is particularly concerning in environments where Windows authentication is prevalent, as it can enable attackers to escalate privileges or move laterally. Given the widespread use of Apache Solr in enterprise search applications across Europe, the vulnerability could impact sectors such as finance, government, healthcare, and telecommunications, where sensitive data is indexed and searched. Failure to mitigate this vulnerability could also affect compliance with European data protection regulations like GDPR due to potential unauthorized data access.

Summary

CVE-2026-22444 is a security vulnerability affecting Apache Solr versions 8.6 through 9.10.0, stemming from improper input validation (CWE-20) in the 'create core' API. Solr's 'allowPaths' setting is designed to restrict filesystem access to specific directories, preventing unauthorized reading of files. However, due to insufficient validation of API parameters, attackers can manipulate the 'create core' API to cause Solr to check and read filesystem paths outside the allowed directories. This can result in the creation of Solr cores using unexpected configuration sets accessible on the filesystem, potentially exposing sensitive data or configurations. On Windows systems configured to allow UNC paths, this vulnerability can lead to the disclosure of NTLM user hashes, which attackers could use for credential theft or lateral movement. The vulnerability is exploitable only if Solr is running in standalone mode, the 'allowPath' restriction is in place, and the 'create core' API is exposed to untrusted users—often due to disabled or misconfigured RuleBasedAuthorizationPlugin permissions. No known exploits are currently reported in the wild. The Apache Software Foundation has addressed this issue in Solr version 9.10.1 and later, recommending users to upgrade and properly configure authorization controls to prevent unauthorized core creation.

CWE-20Improper Input Validation (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #18OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product receives input or data, but it does not validate or incorrectly validates that the input has the properties that are required to process the data safely and correctly.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design · Attack Surface Reduction
Consider using language-theoretic security (LangSec) techniques that characterize inputs using a formal language and build "recognizers" for that language. This effectively requires parsing to be a distinct layer that effectively enforces a boundary between raw input and internal data representations, instead of…
Architecture and Design · Libraries or Frameworks
Use an input validation framework such as Struts or the OWASP ESAPI Validation API. Note that using a framework does not automatically address all input validation problems; be mindful of weaknesses that could arise from misusing the framework itself (CWE-1173).
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter the product, including but not limited to: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any…
OWASP Cheat Sheets
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
Injection Prevention (opens in a new tab)
SQL Injection Prevention (opens in a new tab)
Injection Prevention in Java (opens in a new tab)
OWASP ASVS 4.0.3
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
V5.1.3 (opens in a new tab)
Attack patterns
Buffer Overflow via Environment Variables (opens in a new tab)
Server Side Include (SSI) Injection (opens in a new tab)
Cross Zone Scripting (opens in a new tab)
Command Line Execution through SQL Injection (opens in a new tab)
Object Relational Mapping Injection (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 21 Jan 2026, 14:20 UTC

WeaknessesCWE-20

Technical details

References

Community reviews

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