CVE-2026-40973
HIGHCVE-2026-40973 is a high-severity (CVSS 7) vulnerability in org.springframework.boot:spring-boot. O3 Security confirms whether CVE-2026-40973 is actually reachable in your code before you act, and blocks exploitation at runtime until you patch.
Spring Boot accepts predictable temp directory without ownership verification
Real-World Exposure
org.springframework.boot:spring-boot☕org.springframework.boot:spring-boot☕org.springframework.boot:spring-boot☕org.springframework.boot:spring-boot☕org.springframework.boot:spring-bootReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Maven packages — download data is not available via public APIs for these ecosystems.
Description
A local attacker on the same host as the application may be able to take control of the directory used by ApplicationTemp. When server.servlet.session.persistent is set to true and the attack persists across application restarts, this may allow the attacker to read session information and hijack authenticated users or deploy a gadget chain and execute code as the application's user.
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); predictable temp directory / ApplicationTemp ownership verification. Versions that are no longer supported are also affected per vendor advisory.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| ☕Maven | org.springframework.boot:spring-boot | ≥ 4.0.0&&< 4.0.6 | 4.0.6 |
| ☕Maven | org.springframework.boot:spring-boot | ≥ 3.5.0&&< 3.5.14 | 3.5.14 |
| ☕Maven | org.springframework.boot:spring-boot | ≥ 3.4.0 | No fix |
| ☕Maven | org.springframework.boot:spring-boot | ≥ 3.3.0 | No fix |
| ☕Maven | org.springframework.boot:spring-boot | all versions | No fix |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for org.springframework.boot:spring-boot. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update org.springframework.boot:spring-boot to 4.0.6 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-40973 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether CVE-2026-40973 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to CVE-2026-40973. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2026-40973 in your dependencies?
O3 detects CVE-2026-40973 across Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.