CVE-2025-11230VulnerabilityPublished 19 Nov 2025

CVE-2025-11230: HAProxy Community Edition · Inefficient Algorithmic Complexity

Affects HAProxy Community EditionSource CVE Database V5

Not known to be exploited · CVSS 7.5 High.

Data as of 26 Oct 2026, 06:26 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.

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 Nov 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 2026-10-26.

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
HAProxy Technologies HAProxy Community Edition	Affected =2.4.0 =2.6.0 =2.8.0 =3.0.0 =3.1.0 =3.2.0	Fixed in–

AI-suggested

Until official patches are released, European organizations should implement several targeted mitigations to reduce risk. First, deploy network-level rate limiting and filtering to detect and block abnormal JSON request patterns that could trigger the inefficient parsing. Use web application firewalls (WAFs) or intrusion prevention systems (IPS) configured to identify and mitigate suspicious JSON payloads. Monitor HAProxy logs for unusual spikes in JSON request processing times or resource consumption to enable early detection of exploitation attempts. Consider isolating HAProxy instances behind additional proxy layers or VPNs to restrict exposure to untrusted networks. Regularly update HAProxy to the latest stable versions once patches addressing this vulnerability become available. Engage with HAProxy Technologies and community channels for timely vulnerability disclosures and fixes. Finally, conduct internal audits of HAProxy configurations to ensure minimal exposure of JSON parsing endpoints and enforce strict input validation where possible.

Description

Inefficient algorithm complexity in mjson in HAProxy allows remote attackers to cause a denial of service via specially crafted JSON requests.

Impact

For European organizations, the primary impact of CVE-2025-11230 is the potential for denial of service against critical network infrastructure components. HAProxy is commonly deployed in data centers, cloud environments, and edge networks to manage traffic load and ensure service availability. Exploitation could disrupt web services, internal applications, and APIs, leading to operational downtime and potential financial losses. The lack of confidentiality or integrity impact means data breaches are unlikely, but service interruptions can affect customer trust and compliance with service-level agreements (SLAs). Organizations in sectors such as finance, telecommunications, government, and e-commerce, which rely heavily on HAProxy for traffic management, are at heightened risk. Additionally, the ease of exploitation without authentication increases the threat landscape, as attackers can launch DoS attacks from remote locations without insider access. The absence of known exploits currently provides a window for proactive defense, but the vulnerability’s presence in multiple recent HAProxy versions means many deployments remain exposed.

CWE-407Inefficient Algorithmic Complexity (opens in a new tab)
Class weaknessLikelihood of exploit: Low
An algorithm in a product has an inefficient worst-case computational complexity that may be detrimental to system performance and can be triggered by an attacker, typically using crafted manipulations that ensure that the worst case is being reached.
OWASP Cheat Sheets
File Upload (opens in a new tab)
OWASP ASVS 4.0.3
V12.1.1 (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

haproxy.com/blog/october-2025-cve-2025-11230-haproxy-mjson-library-denial-of-service-vulnerability (opens in a new tab)

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 26 Nov 2025, 09:58 UTC

WeaknessesCWE-407

Technical details

References

Community reviews

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