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CVE-2026-102497· CVE.org (no NVD analysis yet)· CNA apache

Apache XMLSchema: Denial of service through cyclic schema definitions in the schema walker

The Apache XmlSchema walker (xmlschema-walker) doesn't detect cycles in type derivation, substitution groups, model groups or attribute groups. A malicious schema with such a cycle can make the walker recurse until the stack overflows, causing a denial of service. Users are recommended to upgrade to version 2.3.3, which fixes this issue.

HighCVSS 7.5 · v3.1—No exploit Fix available
Published
Sep 29, 2026
Updated
Sep 29, 2026
EPSS
0.4% · 28th percentile
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Report tools

JSON

Action score

30

Monitor

Low priority for now.

CVSS
30 / 40 · 7.5 / 10
CISA KEV
0 / 30 · Not listed
EPSS
0 / 30 · 0.4%

CISA SSVC decision

Exploitation
none
Automatable
yes
Technical impact
partial

Vulnrichment: CISA's decision-tree inputs.

Noroxi analysis

No Noroxi analysis for this record yet

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Affected systems

—

Versions reported by the vendor

Affected version ranges reported by the assigning authority (apache). Independent of NVD's CPE analysis and usually ahead of it.

  • Apache Software Foundation Apache XMLSchema

    • before 2.3.3affected · semver

Same product

apache software foundation: all records

Other highest-scoring records for the same primary product.

  • CVE-2026-102496Apache XMLSchema: Denial of service through deeply nested schema structures
    30Monitor
  • CVE-2026-102495Apache XMLSchema: Denial of service through unbounded recursion when resolving schema imports and includes
    30Monitor

Remediation

Which version to upgrade to

Fix versions compiled from the vendor, package registries and Microsoft. Verify the vendor's note before upgrading.

Product / packageFixed versionSource
Apache Software Foundation Apache XMLSchema2.3.3Vendor (CNA)

Exploit status

No known public exploit

No public exploit has been observed yet. That doesn't mean you're safe, only that the bar is a little higher.

Research context

For pentesters and researchers: attack profile, score disagreement, timeline, patch commits, credits, variant and chain candidates, bug bounty scope. All derived from existing data; no exploit code.

Timeline

From publication to today: proof of concept, Metasploit module, CISA KEV and fix record. Dates are as reported by the sources.

  1. Published
  2. Fix recordedsame day
  3. TodayOct 1, 2026+2 d
EPSS, last 120 days

FIRST EPSS daily score; only changes of 0.01 or more are recorded (step chart).

Patch and commit links

Commit, PR and diff links among the references. A starting point for patch-diffing and variant hunting; fixes, not exploits.

No commit or PR link among the references.

Credits

All researchers

Finders, reporters and analysts named in the CNA record. Click a name for that researcher’s other records.

Variant candidates

Same product, same weakness class, within 18 months. If the patch missed the root cause, the sibling bug is here.

  • CVE-2026-1024950 days apartApache XMLSchema: Denial of service through unbounded recursion when resolving schema imports and includes
    30Monitor
  • CVE-2026-1024960 days apartApache XMLSchema: Denial of service through deeply nested schema structures
    30Monitor

Chain candidates

An authentication bypass and a privilege-requiring bug in the same product, published close together: combined they may become an unauthenticated path.

—

Bug bounty scope

No known public program.

Source: bounty-targets-data (public HackerOne, Bugcrowd, Intigriti, YesWeHack listings).

Technical details

Attack conditions

  • Anyone who can reach it over the internet can trigger it.
  • No account or password is required.
  • No user action is required.
  • No special conditions are required; it is repeatable.

If successful

Confidentiality
none
Integrity
none
Availability
high · the service can be disrupted
Attack vector
Network
Attack complexity
Low
Privileges required
None
User interaction
None
Scope
Unchanged
Confidentiality impact
None
Integrity impact
None
Availability impact
High

Weakness class (CWE)

CWE-674 · Uncontrolled Recursion

CVSS vector

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

nvd-secondary

Attack context

MITRE CAPEC attack patterns and ATT&CK techniques for this weakness class (CWE). A starting point for detection rules and threat hunting.

ATT&CK techniques

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Change log

  1. SSVC exploitation— → none
  2. CVSS— → 7.5
  3. Severity— → high
  4. Exploit maturity— → none
  5. Fix✗ → ✓

For records you follow, these changes also arrive as notifications. →

References

Vendor advisories and official records. Exploit/PoC links are deliberately left out.

All records