mchange-commons-java: Improper Neutralization of Special Elements in Output Used by a Downstream Component
CVE-2026-27727 is a critical-severity improper neutralization of special elements in output used by a downstream component vulnerability in mchange-commons-java from Swaldman, with a CVSS 3.1 base score of 9.8 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. Affected mchange-commons-java versions: < 0.4.0. The record does not name a fixed version, so check the vendor advisory. There is no confirmed exploitation so far. EPSS estimates a 0.98% chance of exploitation within 30 days, higher than 63% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Check which version of mchange-commons-java you run against the affected versions below, and install the vendor's latest release.
- Read the advisory on github.com for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 4.0 | 8.9 | High | CNA (github.com) |
| CVSS 3.1 | 9.8 | Critical | NVD |
| CVSS 3.1 | 8.3 | High | CNA |
Official description
mchange-commons-java, a library that provides Java utilities, includes code that mirrors early implementations of JNDI functionality, including support for remote `factoryClassLocation` values, by which code can be downloaded and invoked within a running application. If an attacker can provoke an application to read a maliciously crafted `jaxax.naming.Reference` or serialized object, they can provoke the download and execution of malicious code. Implementations of this functionality within the JDK were disabled by default behind a System property that defaults to `false`, `com.sun.jndi.ldap.object.trustURLCodebase`. However, since mchange-commons-java includes an independent implementation of JNDI derefencing, libraries (such as c3p0) that resolve references via that implementation could be provoked to download and execute malicious code even after the JDK was hardened. Mirroring the JDK patch, mchange-commons-java's JNDI functionality is gated by configuration parameters that default to restrictive values starting in version 0.4.0. No known workarounds are available. Versions prior to 0.4.0 should be avoided on application CLASSPATHs.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Neutralization of Special Elements in Output Used by a Downstream Component
The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.
How developers prevent this class of flaw
- Programming languages and supporting technologies might be chosen which are not subject to these issues.
- Utilize an appropriate mix of allowlist and denylist parsing to filter control-plane syntax from all input.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: poc, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Patches and release notes
- mchange.com/projects/c3p0/#security-noteRelease Notes
Technical write-ups (may include proof of concept)
- mogwailabs.de/en/blog/2025/02/c3p0-you-little-rascalExploit, Third Party Advisory
Other references
- mchange.com/projects/c3p0/#configuring_securityIssue Tracking
- access.redhat.com/errata/RHSA-2026:14873
- access.redhat.com/errata/RHSA-2026:14874
- access.redhat.com/errata/RHSA-2026:18054
- access.redhat.com/errata/RHSA-2026:18055
- access.redhat.com/errata/RHSA-2026:18059
- access.redhat.com/errata/RHSA-2026:34365
- access.redhat.com/errata/RHSA-2026:3890
- access.redhat.com/errata/RHSA-2026:4285
- access.redhat.com/security/cve/CVE-2026-27727
- bugzilla.redhat.com/show_bug.cgi?id=2442671
- security.access.redhat.com/data/csaf/v2/vex/2026/cve-2026-27727.json
Other vulnerabilities in mchange-commons-java
- 7.1 High severity
Recent Improper Neutralization of Special Elements in Output Used by a Downstream Component vulnerabilities
- 9.6 Critical severity
- 7.3 High severity
- 9.8 Critical severity
- 7.1 High severity
- 9.8 Critical severity
- 9.8 Critical severity
Spotted an error? Tell us.