Security readout for executives and security teams
Plain-English summary
AssertJ, a Java testing assertion library, can parse XML unsafely in specific assertion and formatting methods. If a project feeds attacker-controlled XML into those methods, the parser may expose local files, trigger internal network requests, or cause resource exhaustion. This is most urgent for CI, test harnesses, or tools that evaluate untrusted XML.
Executive priority
Prioritize remediation where AssertJ is used in CI, testing services, or tooling that processes user-supplied XML. For internal-only tests with fixed XML fixtures, urgency is lower, but upgrading remains prudent because the affected API is deprecated and slated for removal.
Technical view
CVE-2026-24400 is a CWE-611 XXE issue in AssertJ versions 1.4.0 through before 3.27.7. `XmlStringPrettyFormatter.toXmlDocument(String)` uses default `DocumentBuilderFactory` settings. It is reached via `isXmlEqualTo(CharSequence)` and `xmlPrettyFormat(String)` when processing untrusted XML. AssertJ recommends XMLUnit, upgrading to 3.27.7, or avoiding these methods with untrusted input.
Likely exposure
Exposure is limited to Java/JVM projects using affected AssertJ versions and passing untrusted XML into `isXmlEqualTo(CharSequence)` or `xmlPrettyFormat(String)`. Many uses of AssertJ in ordinary unit tests may not be exposed if inputs are static and trusted.
Exploitation context
No active exploitation is indicated in the provided sources, and the CVE is not marked KEV. Successful abuse requires a path where an attacker can influence XML processed by the affected AssertJ methods, typically in tests, validation tooling, CI jobs, or developer-facing utilities.
Researcher notes
The advisory identifies version range, affected methods, impact classes, and preferred remediation. Evidence does not show broad runtime exposure by default; reachability analysis is essential. The CVSS vector indicates local attack vector and low complexity, but business risk depends heavily on whether untrusted XML reaches these testing utilities.
Mitigation direction
- Replace `isXmlEqualTo(CharSequence)` with XMLUnit where practical.
- Upgrade AssertJ to version 3.27.7 or later.
- Avoid affected methods with untrusted XML input.
- Review vendor advisory and release notes for project-specific guidance.
- Apply OWASP XXE prevention guidance where XML parsing remains necessary.
Validation and detection
- Inventory AssertJ versions in Java/JVM dependency manifests.
- Search code for `isXmlEqualTo(CharSequence)` usage.
- Search code for `XmlStringPrettyFormatter` or `xmlPrettyFormat(String)` usage.
- Determine whether any matching usage receives untrusted XML.
- Confirm upgraded builds resolve AssertJ below 3.27.7.
- Verify replacement XML comparisons use hardened XML parsing defaults.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
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CWE-611: Exact CWE lookup
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Open ATT&CK lookupCloud metadata behavior lookup
The CVE wording references SSRF or metadata access, so cloud discovery and credential material review may help. This is a Glexia inferred lookup path, not an official MITRE, ATT&CK, or CVE Program mapping.
Open ATT&CK lookupCVE-2026-24400 mapping review
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Open ATT&CK lookup- Severity
- High
- CVSS
- 8.2 (4.0)
- Known Exploited
- No
- Published
Vector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:L/SC:H/SI:N/SA:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:L/SC:H/SI:N/SA:N——Primary CVE scoreVulnerability scoring details
Base CVSS 4.0 score
8.2HighVector: CVSS:4.0/AV:L/AC:L/AT:N/PR:L/UI:N/VC:H/VI:N/VA:L/SC:H/SI:N/SA:N
Source materials
- CVE List V5 sourceCVE List V5
- https://github.com/assertj/assertj/security/advisories/GHSA-rqfh-9r24-8c9rCVE reference · x_refsource_CONFIRM
- https://github.com/assertj/assertj/commit/85ca7eb6609bb179c043b85ae7d290523b1ba79aCVE reference · x_refsource_MISC
- https://cheatsheetseries.owasp.org/cheatsheets/XML_External_Entity_Prevention_Cheat_Sheet.htmlCVE reference · x_refsource_MISC
- https://github.com/assertj/assertj/releases/tag/assertj-build-3.27.7CVE reference · x_refsource_MISC
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.
Improper Restriction of XML External Entity Reference
Improper Restriction of XML External Entity Reference represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.