CVE-2024-40857VulnerabilityPublished 16 Sep 2024Updated 2 Apr 2026

CVE-2024-40857: Apple Safari · Processing maliciously crafted web content may lead to universal cross site scripting

Affects Apple SafariSource CVE Database V5

Not known to be exploited · CVSS 6.1 Medium.

Data as of 26 Oct 2026, 07:57 UTC

CVSS 3.1 base score

6.1Medium

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

EPSS: 0.5% chance of exploitation in 30 days – higher than 45% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

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

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: Required: Successful exploitation of this vulnerability requires a user to take some action before the vulnerability can be exploited.
Scope: Changed: An exploited vulnerability can affect resources beyond the security scope managed by the security authority of the vulnerable component. In this case, the vulnerable component and the impacted component are different and managed by different security authorities.
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 impacted component.
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 on the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 16 Sep 2024
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
Apple Safari	Affected =0	Fixed in–

AI-suggested

To mitigate CVE-2024-40857, organizations and users should immediately update Safari to version 18 or later and ensure all Apple devices are running the latest OS versions: iOS 18, iPadOS 18, macOS Sequoia 15, tvOS 18, visionOS 2, and watchOS 11. Beyond patching, organizations should implement strict web content filtering and URL reputation services to block access to known malicious sites. Employing browser security features such as Content Security Policy (CSP) can help limit the impact of XSS attacks by restricting script execution sources. User education on phishing and suspicious links is critical since exploitation requires user interaction. Network-level protections like DNS filtering and intrusion detection systems tuned for web-based attacks can provide additional defense layers. For enterprise environments, consider deploying endpoint protection solutions that monitor browser behavior for anomalies. Regularly audit and monitor logs for unusual web activity or script execution patterns. Finally, encourage users to use multi-factor authentication on sensitive web services to reduce the impact of session hijacking attempts.

Description

This issue was addressed through improved state management. This issue is fixed in Safari 18, iOS 18 and iPadOS 18, macOS Sequoia 15, tvOS 18, visionOS 2, watchOS 11. Processing maliciously crafted web content may lead to universal cross site scripting.

Impact

The primary impact of CVE-2024-40857 is on the confidentiality and integrity of user data accessed through Safari on Apple devices. Successful exploitation allows attackers to execute arbitrary scripts in the context of trusted websites, potentially leading to theft of cookies, session tokens, or other sensitive information. This can facilitate account takeover, unauthorized actions on web applications, and further malware delivery. Since Safari is the default browser on Apple platforms, a large user base is exposed, including consumers, enterprises, and government users. The vulnerability’s universal XSS nature means it can bypass same-origin policy protections, increasing the risk of widespread exploitation. Although no availability impact is noted, the breach of confidentiality and integrity can have severe consequences such as data leakage, fraud, and reputational damage. Organizations with Apple device fleets, especially those handling sensitive or regulated data, face increased risk if patches are not applied promptly. The requirement for user interaction means social engineering or phishing campaigns could be used to trigger the exploit.

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') (opens in a new tab)
Base weaknessLikelihood of exploit: HighCWE Top 25 (2025): #1OWASP Top 10 A05:2025: Injection (opens in a new tab)
The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users.
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.
Implementation · Architecture and Design
Understand the context in which your data will be used and the encoding that will be expected. This is especially important when transmitting data between different components, or when generating outputs that can contain multiple encodings at the same time, such as web pages or multi-part mail messages.
Architecture and Design · Implementation · Attack Surface Reduction
Understand all the potential areas where untrusted inputs can enter your software: parameters or arguments, cookies, anything read from the network, environment variables, reverse DNS lookups, query results, request headers, URL components, e-mail, files, filenames, databases, and any external systems that provide…
OWASP Cheat Sheets
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Injection Prevention (opens in a new tab)
Abuse Case (opens in a new tab)
Deserialization (opens in a new tab)
OWASP ASVS 4.0.3
V5.3.3 (opens in a new tab)
V1.5.1 (opens in a new tab)
Attack patterns
XSS Using MIME Type Mismatch (opens in a new tab)
DOM-Based XSS (opens in a new tab)
Reflected XSS (opens in a new tab)
Stored XSS (opens in a new tab)
Cross-Site Scripting (XSS) (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 2 Apr 2026, 23:40 UTC

WeaknessesCWE-79

Technical details

References

Community reviews

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