VulnerabilityPublished 7 Aug 2025

CVE-2025-8533: Flexibits Fantastical · Incorrect Authorization

Affects Flexibits FantasticalSource CVE Database V5

Not known to be exploited · CVSS 6.9 Medium · fixed in 4.0.16 : update Flexibits Fantastical when convenient.

Data as of 26 Oct 2026, 10:12 UTC

CVSS 4.0 base score

6.9Medium

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 32% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 4.0.16

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:L/VI:L/VA:N/SC:N/SI:N/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: Low
Vulnerable system integrity: Low
Vulnerable system availability: None
Subsequent system confidentiality: None
Subsequent system integrity: None
Subsequent system availability: None

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

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, 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: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the Vulnerable System.
Vulnerable system integrity: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact to the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system confidentiality: None: There is no loss of confidentiality within the Subsequent System or all confidentiality impact is constrained to the Vulnerable System.
Subsequent system integrity: None: There is no loss of integrity within the Subsequent System or all integrity impact is constrained to the Vulnerable System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 7 Aug 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
Flexibits Fantastical	Affected =0	Fixed in–

AI-suggested

To mitigate CVE-2025-8533, European organizations should prioritize updating Fantastical to version 4.0.16 or later, where the authorization checks have been properly implemented. Beyond patching, organizations should enforce strict endpoint security controls to prevent unauthorized local code execution, including application whitelisting, endpoint detection and response (EDR) solutions, and least privilege policies to limit the ability of unprivileged processes to run arbitrary code. Network segmentation and access controls should be applied to reduce the risk of lateral movement that could lead to local access on devices running Fantastical. Additionally, organizations should audit and monitor local process activities on critical endpoints to detect unusual interactions with XPC services. User education on the risks of executing untrusted software locally can further reduce exploitation likelihood. For environments with shared devices, implementing session isolation and user access controls can limit exposure. Finally, organizations should review Fantastical usage policies and consider alternative calendar solutions if the risk profile is unacceptable.

Description

A vulnerability was identified in the XPC services of Fantastical. The services failed to implement proper client authorization checks in its listener:shouldAcceptNewConnection method, unconditionally accepting requests from any local process. As a result, any local, unprivileged process could connect to the XPC service and access its methods. This issue has been resolved in version 4.0.16.

Impact

For European organizations, the impact of CVE-2025-8533 depends largely on the deployment of Fantastical within their environments. Fantastical is a popular calendar and scheduling application, often used on macOS and iOS devices. Organizations relying on Fantastical for critical scheduling or collaboration could face risks if local attackers gain access to user machines, especially in shared or less controlled environments such as hot-desking offices or public access terminals. The vulnerability could enable unauthorized local processes to interact with Fantastical's XPC services, potentially exposing sensitive calendar data or enabling unauthorized actions within the app. While the vulnerability does not allow remote exploitation, insider threats or malware with local execution capabilities could leverage this flaw to escalate access or exfiltrate information. This is particularly relevant for organizations with high compliance requirements around data confidentiality, such as those in finance, healthcare, or government sectors. Additionally, the lack of user interaction and privileges required for exploitation increases the risk in environments where endpoint security is weak or where users may inadvertently execute malicious code locally. The vulnerability’s resolution in version 4.0.16 means that organizations not promptly updating may remain exposed.

CWE-863Incorrect Authorization (opens in a new tab)
Class weaknessLikelihood of exploit: HighCWE Top 25 (2025): #17OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The product performs an authorization check when an actor attempts to access a resource or perform an action, but it does not correctly perform the check.
Architecture and Design
Divide the product into anonymous, normal, privileged, and administrative areas. Reduce the attack surface by carefully mapping roles with data and functionality. Use role-based access control (RBAC) to enforce the roles at the appropriate boundaries.
Architecture and Design
Ensure that access control checks are performed related to the business logic. These checks may be different than the access control checks that are applied to more generic resources such as files, connections, processes, memory, and database records.
Architecture and Design · Libraries or Frameworks
Use a vetted library or framework that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
OWASP Cheat Sheets
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.8 (opens in a new tab)
V13.4.2 (opens in a new tab)
V7.2.2 (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

Affected software

Description

AI analysisMachine-generated, updated 7 Aug 2025, 10:32 UTC

WeaknessesCWE-863

Technical details

References

Community reviews

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