High severity · published Aug 21, 2026
CVE-2026-59279
Unbounded persistent session allocation via repeated initialize requests
7.5
CVSS
0.5%
EPSS
No
On KEV
Description
The MCP Streamable HTTP server transport (WebFlux and WebMvc variants) does not place any limit on the number of sessions it retains, and by default does not require clients to be authenticated. As a result, a remote attacker can cause the server to accumulate an unbounded number of sessions over time, gradually exhausting available memory and ultimately causing a Denial of Service that affects all legitimate clients.
Affected versions:
Spring AI: 2.0.0
CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Attack vector
Network
Complexity
Low
Privileges
None
User interaction
None
Confidentiality
None
Integrity
None
Availability
High
Scope
Unchanged
Exploitation
Is it being used?
Exploit prediction (EPSS)0.5% · higher than 46% of CVEs
Exploited in the wildNo evidence yet
CISA KEVNot listed
Ransomware campaign useNot known
Affected products
Which versions
SA
Spring AI · Spring
2.0.0 · source: vendor, NVD
References
NVD
https://nvd.nist.gov/vuln/detail/CVE-2026-59279
CVE.org
https://www.cve.org/CVERecord?id=CVE-2026-59279
Vendor Advisory
https://spring.io/security/cve-2026-59279
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