CVE-2025-53506 | Apache Tomcat: DoS via excessive h2 streams at connection start

Uncontrolled Resource Consumption vulnerability in Apache Tomcat if an HTTP/2 client did not acknowledge the initial settings frame that reduces the maximum permitted concurrent streams. This issue affects Apache Tomcat: from 11.0.0-M1 through 11.0.8, from 10.1.0-M1 through 10.1.42, from 9.0.0.M1 through 9.0.106. The following versions were EOL at the time the CVE was created but are known to be affected: 8.5.0 through 8.5.100. Other EOL versions may also be affected. Users are recommended to upgrade to version 11.0.9, 10.1.43 or 9.0.107, which fix the issue.

Published: 2025-07-10 Last update: 2025-11-04 Assigner: [email protected] Source: [email protected]
NVD Status：Modified，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2025-53506 is rated Moderate Risk (58.6/100): CVSS High severity, with medium exploitation likelihood (EPSS 1.25%). Review affected assets and schedule remediation.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Exploit prediction scoring system (EPSS) score for CVE-2025-53506

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-05-06 0.43% 1.25% +0.82%
2 2026-04-05 0.32% 0.43% +0.11%
3 2026-03-26 — 0.32% —

Full EPSS history (12 records total)

Common vulnerability scoring system (CVSS) metrics for CVE-2025-53506

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 134c704f-9b21-4f2e-91b3-4a467353bcc0

Weakness enumeration for CVE-2025-53506

GitHub Security Advisory for CVE-2025-53506

GHSA-25xr-qj8w-c4vf · Severity: high · Ecosystem: maven — Apache Tomcat Coyote vulnerable to Denial of Service via excessive HTTP/2 streams

OS Trackers for CVE-2025-53506

vendor priority summary link
debian not yet assigned CVE-2025-53506 not yet assigned priority: Debian including 3 source packages (tomcat10, tomcat11, tomcat9), 12 status rows across 5 suites (bookworm, bullseye, forky, sid, trixie): resolved 12. https://security-tracker.debian.org/tracker/CVE-2025-53506
redhat medium — https://access.redhat.com/security/cve/CVE-2025-53506
suse medium — https://www.suse.com/security/cve/CVE-2025-53506/
ubuntu medium CVE-2025-53506 medium priority: Ubuntu including 6 source packages (tomcat10, tomcat11, tomcat6, tomcat7, tomcat8, tomcat9), 41 status rows across 9 suites (bionic, focal, jammy, noble, plucky, questing, trusty, upstream, xenial): DNE 18, ignored 11, needed 6, not-affected 3, released 3. https://ubuntu.com/security/CVE-2025-53506

Affected software / configurations for CVE-2025-53506

Vendor Product Version Raw CPE
apache tomcat >= 9.0.0, <= 9.0.106 cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:*
apache tomcat >= 10.1.0, <= 10.1.42 cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:*
apache tomcat >= 11.0.0, <= 11.0.8 cpe:2.3:a:apache:tomcat:*:*:*:*:*:*:*:*

References for CVE-2025-53506

cvelogic Threat Intelligence