What’s Vulnerable › Vulnerabilities

CVE-2026-40988: Unbounded DEFLATE Inflation in SAML 2.0 Service Provider

• Severity: high (CVSS 7.5 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-06-09 · updated 2026-07-23
• Weakness: CWE-400

Description

An application using spring-security-saml2-service-provider and the REDIRECT binding for SAML 2.0 Login or Logout may be vulnerable to a denial of service by way of an unbounded writer that inflates the compressed SAML payload into memory. Affected versions: Spring Security 5.7.0 through 5.7.23; 5.8.0 through 5.8.25; 6.3.0 through 6.3.16; 6.4.0 through 6.4.16; 6.5.0 through 6.5.10; 7.0.0 through 7.0.5.

Affected products

• Spring Security: from 5.7.0 before 5.7.24; from 5.8.0 before 5.8.26; from 6.3.0 before 6.3.17; from 6.4.0 before 6.4.17; from 6.5.0 before 6.5.10.2; from 7.0.0 before 7.0.5.1 — fixed in 5.7.24, 5.8.26, 6.3.17, 6.4.17, 6.5.10.2, 7.0.5.1
• Spring Security: from 5.7.0 before 5.7.24; from 5.8.0 before 5.8.26; from 6.3.0 before 6.3.17; from 6.4.0 before 6.4.17; from 6.5.0 before 6.5.10.2; from 7.0.0 before 7.0.5.1 — fixed in 5.7.24, 5.8.26, 6.3.17, 6.4.17, 6.5.10.2, 7.0.5.1

How to fix

Upgrade to a fixed version: Spring Security 5.7.24, 5.8.26, 6.3.17, 6.4.17; Spring Security 5.7.24, 5.8.26, 6.3.17, 6.4.17. Check the vendor advisory for mitigations.

References

• https://spring.io/security/cve-2026-40988

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