Apache CXF: Concurrent Execution using Shared Resource with Improper Synchronization
CVE-2026-97791 is a high-severity concurrent execution using shared resource with improper synchronization vulnerability in Apache CXF from Apache, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 4.2.4, 4.1.9, 3.6.13 as the first without the flaw, so updating Apache CXF to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.3% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Apache CXF to 4.2.4 or 4.1.9 or 3.6.13, whichever matches your release line, or a later version.
- Update Cxf to 3.6.13 or 4.1.9 or 4.2.4, whichever matches your release line, or a later version.
- Read the advisory on lists.apache.org 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
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Apache | Apache CXF | 4.2.0 up to, but not including, 4.2.4; 4.0.0 up to, but not including, 4.1.9; before 3.6.13 | 4.2.4, 4.1.9, 3.6.13 |
| Apache | Cxf | before 3.6.13; 4.0.0 up to, but not including, 4.1.9; 4.2.0 up to, but not including, 4.2.4 | 3.6.13, 4.1.9, 4.2.4 |
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
- NoneNo data is disclosed.
- Integrity
- NoneNothing can be modified.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H. Scored by CISA (ADP).
Official description
In Apache CXF, STSTokenValidator checks whether a SAML assertion is signed by a trusted certificate before deciding to send it to the STS. That result was stored in one object shared by all requests, so one request could read another's result. A remote, unauthenticated attacker could send a forged assertion signed with an untrusted certificate while legitimate requests were being processed, and it could be accepted as trusted without ever reaching the STS. Only services that use STSTokenValidator to validate SAML tokens without alwaysValidateToSts set are affected. Users are recommended to upgrade to versions 4.2.4 or 4.1.9 or 3.6.13, which fix this issue.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Concurrent Execution using Shared Resource with Improper Synchronization
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
How developers prevent this class of flaw
- In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
- Use thread-safe capabilities such as the data access abstraction in Spring.
- Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring. Additionally, this will minimize the amount of synchronization necessary and may even help to reduce the likelihood of a denial of service where an attacker may be able to repeatedly trigger a critical section (CWE-400).
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Third-party and government advisories
- openwall.com/lists/oss-security/2026/10/09/10Mailing List, Third Party Advisory
Other vulnerabilities in Apache CXF
- 9.1 Critical severity
- 7.5 High severity
- 7.5 High severity
- 8.1 High severity
- 9.1 Critical severity
- 7.5 High severity
Recent Concurrent Execution using Shared Resource with Improper Synchronization vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 7.0 High severity
- 8.3 High severity
- 8.3 High severity
- 8.8 High severity
Spotted an error? Tell us.