Spring Boot: Observable Timing Discrepancy
CVE-2026-40972 is a high-severity observable timing discrepancy vulnerability in Spring Boot from Spring, with a CVSS 3.1 base score of 7.5 out of 10. It can be exploited from the same local network by an unauthenticated attacker, without any action from a user. The record lists versions 4.0.6, 3.5.14, 3.4.16 as the first without the flaw, so updating Spring Boot to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.26% 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 Spring Boot to 4.0.6 or 3.5.14 or 3.4.16 or 3.3.19, whichever matches your release line, or a later version.
- Read the advisory on spring.io for workarounds and exact fixed builds.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Spring | Spring Boot | 4.0.0 up to, but not including, 4.0.6; 3.5.0 up to, but not including, 3.5.14; 3.4.0 up to, but not including, 3.4.16; 3.3.0 up to, but not including, 3.3.19; 2.7.0 up to, but not including, 2.7.33 | 4.0.6, 3.5.14, 3.4.16, 3.3.19, 2.7.33 |
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
- AdjacentThe attacker must be on the same local network segment.
- Attack complexity
- HighSuccess depends on conditions outside the attacker's control.
- 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:A/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H. Scored by CNA (vmware.com).
Official description
An attacker on the same network as the remote application may be able to utilize a timing attack to discover information about the remote secret. In extreme circumstances this could result in the attacker determining the secret and uploading changed classes, thereby achieving remote code execution in the remote application. Affected: Spring Boot 4.0.0–4.0.5 (fix 4.0.6), 3.5.0–3.5.13 (fix 3.5.14), 3.4.0–3.4.15 (fix 3.4.16), 3.3.0–3.3.18 (fix 3.3.19), 2.7.0–2.7.32 (fix 2.7.33); DevTools remote secret comparison. Versions that are no longer supported are also affected per vendor advisory.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Observable Timing Discrepancy
Two separate operations in a product require different amounts of time to complete, in a way that is observable to an actor and reveals security-relevant information about the state of the product, such as whether a particular operation was successful or not.
More Observable Timing Discrepancy vulnerabilities (CWE-208)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Other vulnerabilities in Spring Boot
- 9.1 Critical severity
- 7.5 High severity
- 9.8 Critical severity
- 7.0 High severity
- 9.1 Critical severity
- 8.1 High severity
Recent Observable Timing Discrepancy vulnerabilities
- 7.5 High severity
- 7.5 High severity
- 7.4 High severity
- 7.4 High severity
- 8.5 High severity
- 8.6 High severity
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