VulnerabilityPublished 19 Jun 2025Updated 20 Jun 2025

CVE-2025-49763: Apache Traffic Server · Uncontrolled Resource Consumption

Affects Apache Traffic ServerSource CVE Database V5

Not known to be exploited · CVSS 7.5 High · fixed in 9.2.11 : patch Apache Traffic Server soon.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.7% chance of exploitation in 30 days – higher than 54% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 9.2.11

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 19 Jun 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 or the CVSS exploit maturity 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
Apache Software Foundation Apache Traffic Server	Affected =10.0.0 =9.0.0	Fixed in–

AI-suggested

Beyond upgrading to Apache Traffic Server versions 9.2.11 or 10.0.6 or later, European organizations should implement the following specific mitigations: 1) Immediately configure the --max-inclusion-depth setting to a conservative value appropriate to the organization's typical ESI usage patterns to limit recursion depth and prevent resource exhaustion. 2) Employ network-level protections such as Web Application Firewalls (WAFs) or Intrusion Prevention Systems (IPS) to detect and block anomalous or excessively nested ESI requests. 3) Monitor server resource utilization closely, setting alerts for unusual memory consumption spikes that could indicate attempted exploitation. 4) Conduct regular audits of ESI usage and plugin configurations to ensure no unauthorized or unexpected changes have been made. 5) Isolate Apache Traffic Server instances handling untrusted or external traffic from critical internal networks to contain potential impact. 6) Implement rate limiting on incoming requests to reduce the risk of automated exploitation attempts. 7) Maintain an incident response plan that includes procedures for mitigating resource exhaustion attacks to minimize downtime.

Description

ESI plugin does not have the limit for maximum inclusion depth, and that allows excessive memory consumption if malicious instructions are inserted. Users can use a new setting for the plugin (--max-inclusion-depth) to limit it. This issue affects Apache Traffic Server: from 10.0.0 through 10.0.5, from 9.0.0 through 9.2.10. Users are recommended to upgrade to version 9.2.11 or 10.0.6, which fixes the issue.

Impact

For European organizations, the impact of this vulnerability can be significant, particularly for those relying on Apache Traffic Server for web acceleration, caching, and proxy services. Exploitation could lead to denial of service by exhausting memory resources, resulting in service outages or degraded performance. This can affect critical web infrastructure, including content delivery networks (CDNs), e-commerce platforms, and public-facing government or financial services portals. The disruption could lead to loss of availability, impacting business continuity and customer trust. Additionally, resource exhaustion attacks may serve as a smokescreen for other malicious activities or be leveraged in multi-vector attacks. Given the role of Apache Traffic Server in handling large volumes of web traffic, the scope of impact can be broad, affecting multiple services and users simultaneously. The absence of authentication requirements or user interaction for triggering the vulnerability increases the risk, as attackers can exploit it remotely by sending crafted ESI instructions to vulnerable servers.

CWE-400Uncontrolled Resource Consumption (opens in a new tab)
Class weaknessLikelihood of exploit: High
The product does not properly control the allocation and maintenance of a limited resource.
MITRE discourages mapping vulnerabilities to this broad entry; the root cause is usually a more specific weakness.
Architecture and Design
Design throttling mechanisms into the system architecture. The best protection is to limit the amount of resources that an unauthorized user can cause to be expended. A strong authentication and access control model will help prevent such attacks from occurring in the first place.
Architecture and Design
Mitigation of resource exhaustion attacks requires that the target system either: recognizes the attack and denies that user further access for a given amount of time, or; uniformly throttles all requests in order to make it more difficult to consume resources more quickly than they can again be freed.
Architecture and Design
Ensure that protocols have specific limits of scale placed on them.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
Attack patterns
XML Ping of the Death (opens in a new tab)
Regular Expression Exponential Blowup (opens in a new tab)
Sustained Client Engagement (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

lists.apache.org/thread/15t32nxbypqg1m2smp640vjx89o6v5f8 (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 19 Jun 2025, 10:31 UTC

WeaknessesCWE-400

Technical details

References

Community reviews

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