VulnerabilityPublished 10 Jul 2025Updated 4 Nov 2025

CVE-2025-52434: Apache Tomcat · Race Condition

Affects Apache TomcatSource CVE Database V5

Not known to be exploited · CVSS 7.5 High · fixed in 9.0.107 : patch Apache Tomcat soon.

Data as of 26 Oct 2026, 09:15 UTC

CVSS 3.1 base score

7.5High

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 2.0% chance of exploitation in 30 days – higher than 81% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 9.0.107

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: None
Availability: High

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 10 Jul 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
Mavenorg.apache.tomcat/tomcat`pkg:maven/org.apache.tomcat/tomcat`Other threats	Affected 8.5.0 <=8.5.100	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

1. Upgrade all affected Apache Tomcat instances to version 9.0.107 or later immediately to apply the official fix. 2. For environments unable to upgrade promptly, consider disabling the APR/Native connector or HTTP/2 support temporarily to mitigate exposure. 3. Implement network-level protections such as rate limiting and connection throttling to reduce the risk of exploitation via rapid connection closures. 4. Monitor server logs and network traffic for unusual patterns of HTTP/2 connection terminations or errors indicative of race condition triggers. 5. Conduct thorough testing of web applications post-upgrade to ensure stability and compatibility with the patched Tomcat version. 6. Maintain an inventory of Apache Tomcat deployments and their versions to prioritize patching efforts effectively. 7. Engage in proactive vulnerability management and incident response planning to quickly address potential exploitation attempts.

Description

Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') vulnerability in Apache Tomcat when using the APR/Native connector. This was particularly noticeable with client initiated closes of HTTP/2 connections. This issue affects Apache Tomcat: 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, older, EOL versions may also be affected. Users are recommended to upgrade to version 9.0.107, which fixes the issue.

Impact

For European organizations, this vulnerability poses a significant risk to the availability of web services hosted on Apache Tomcat servers using the APR/Native connector with HTTP/2 enabled. Disruption of critical web applications, internal portals, or APIs could lead to operational downtime, affecting business continuity and service delivery. Sectors such as finance, government, healthcare, and telecommunications, which heavily rely on Apache Tomcat for scalable web infrastructure, may experience service outages or degraded performance. The lack of confidentiality or integrity impact reduces the risk of data breaches, but denial of service can indirectly affect trust and compliance with service-level agreements (SLAs). Given the remote and unauthenticated exploit vector, attackers could potentially cause widespread disruption if the vulnerability is weaponized, especially in environments with high HTTP/2 traffic.

Summary

CVE-2025-52434 is a concurrency vulnerability classified under CWE-362, affecting the Apache Tomcat server's APR/Native connector component. The vulnerability manifests as a race condition due to improper synchronization when handling concurrent HTTP/2 connections, specifically during client-initiated connection closures. This flaw exists in Apache Tomcat versions from 9.0.0.M1 through 9.0.106 and in older 8.5.x versions (8.5.0 through 8.5.100), including some end-of-life releases. The race condition can lead to resource state inconsistencies, causing denial of service by crashing or destabilizing the server or causing it to become unresponsive. The vulnerability does not impact confidentiality or integrity but severely affects availability. It can be exploited remotely without authentication or user interaction, increasing its risk profile. Although no active exploits are reported, the CVSS score of 7.5 (high) reflects the potential impact and ease of exploitation. The issue is resolved in Apache Tomcat 9.0.107, which includes proper synchronization fixes in the APR/Native connector to handle concurrent HTTP/2 connection closures safely.

CWE-362Concurrent Execution using Shared Resource with Improper Synchronization ('Race Condition') (opens in a new tab)
Class weaknessLikelihood of exploit: MediumOWASP Top 10 A06:2025: Insecure Design (opens in a new tab)
The product contains a concurrent code sequence that requires temporary, exclusive access to a shared resource, but a timing window exists in which the shared resource can be modified by another code sequence operating concurrently.
Architecture and Design
In languages that support it, use synchronization primitives. Only wrap these around critical code to minimize the impact on performance.
Architecture and Design
Use thread-safe capabilities such as the data access abstraction in Spring.
Architecture and Design
Minimize the usage of shared resources in order to remove as much complexity as possible from the control flow and to reduce the likelihood of unexpected conditions occurring.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
Secure Design Principles (opens in a new tab)
OWASP ASVS 4.0.3
V1.11.2 (opens in a new tab)
Attack patterns
Leveraging Time-of-Check and Time-of-Use (TOCTOU) Race Conditions (opens in a new tab)
Leveraging Race Conditions (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 5 Nov 2025, 15:47 UTC

WeaknessesCWE-362

Technical details

References

Community reviews

Related threats