VulnerabilityPublished 9 Jul 2025Updated 22 Jul 2025

CVE-2025-53645: Zimbra Collaboration · Uncontrolled Resource Consumption

Source CVE Database V5

Not known to be exploited · CVSS 7.5 High · fixed in 10.1.9 : patch affected systems soon.

Data as of 26 Oct 2026, 11:07 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 1.6% chance of exploitation in 30 days – higher than 75% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 10.1.9, 10.0.15

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 9 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 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

AI-suggested

To mitigate this vulnerability effectively, European organizations should prioritize the following actions: 1) Immediate patching: Upgrade Zimbra Collaboration Suite to versions 9.0.0 Patch 46, 10.0.15, 10.1.9 or later, as these contain fixes addressing the improper handling of excessive path segments. 2) Network-level protections: Implement rate limiting and request size restrictions on firewalls or reverse proxies in front of the Zimbra Admin Console to detect and block abnormal GET requests with excessive comma-separated path segments. 3) Access controls: Restrict access to the Admin Console interface to trusted IP addresses or VPNs to reduce exposure to unauthenticated remote attackers. 4) Monitoring and alerting: Deploy monitoring tools to detect unusual spikes in resource consumption or anomalous HTTP request patterns targeting the Admin Console. 5) Incident response readiness: Prepare playbooks for DoS scenarios affecting Zimbra services to enable rapid mitigation and recovery. 6) Vendor communication: Stay informed via Zimbra security advisories and subscribe to vulnerability notifications to ensure timely awareness of patches and emerging threats. These targeted mitigations go beyond generic advice by focusing on both patch management and proactive network-level defenses tailored to the nature of this vulnerability.

Description

Zimbra Collaboration (ZCS) before 9.0.0 Patch 46, 10.0.x before 10.0.15, and 10.1.x before 10.1.9 is vulnerable to a denial of service condition due to improper handling of excessive, comma-separated path segments in the Admin Console. An unauthenticated remote attacker can send specially crafted GET requests that trigger redundant processing and inflated responses. This leads to uncontrolled resource consumption, resulting in denial of service.

Impact

For European organizations, the impact of this vulnerability can be substantial. Zimbra Collaboration Suite is widely used by enterprises, educational institutions, and government agencies across Europe for email, calendaring, and collaboration. A successful DoS attack exploiting this vulnerability could disrupt critical communication channels, impair administrative access to the mail system, and degrade overall productivity. In sectors such as finance, healthcare, and public administration, where timely and reliable communication is essential, such outages could lead to operational delays, compliance issues, and reputational damage. Additionally, denial of service on the Admin Console could delay incident response and remediation efforts during an attack, exacerbating the impact. Given that the attack requires no authentication and can be launched remotely, threat actors could easily target vulnerable Zimbra servers to cause widespread disruption. This risk is heightened in environments where patching cycles are slow or where legacy Zimbra versions remain in use.

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

Community reviews

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Exploitation evidence

What to do

Description

AI analysisMachine-generated, updated 22 Jul 2025, 20:15 UTC

WeaknessesCWE-400

Technical details

References

Community reviews

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