VulnerabilityPublished 25 Mar 2026Updated 2 Apr 2026

CVE-2026-20639: Apple macOS · Integer Overflow

Affects Apple macOSSource CVE Database V5

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Not known to be exploited · CVSS 7.5 High · fixed in 26.3 : patch Apple macOS soon.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

7.5High

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

EPSS: 0.6% chance of exploitation in 30 days – higher than 49% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 26.3, 15.7.5, 14.8.5

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 25 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 30 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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), 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

Upgrade Apple macOS to 26.3, 15.7.5 or 14.8.5.

Affected software

Product	Affected	Fixed in
ApplemacOS	Affected <26.3	Fixed in 26.3
ApplemacOS	Affected <15.7.5	Fixed in 15.7.5
ApplemacOS	Affected <14.8.5	Fixed in 14.8.5

AI-suggested

Organizations should immediately apply the security updates provided by Apple in macOS Sequoia 15.7.5, Sonoma 14.8.5, and Tahoe 26.3 to remediate this vulnerability. Beyond patching, network-level protections such as firewall rules should restrict unnecessary inbound traffic to macOS systems to reduce exposure. Employing intrusion detection and prevention systems (IDPS) with updated signatures can help detect attempts to exploit this vulnerability. Regularly auditing and minimizing the attack surface by disabling unused services on macOS devices will further reduce risk. Security teams should monitor threat intelligence feeds for any emerging exploit code targeting CVE-2026-20639. Implementing application whitelisting and system integrity monitoring can help detect anomalous behavior resulting from exploitation attempts. Finally, organizations should ensure robust backup and recovery procedures are in place to mitigate potential denial of service impacts.

Description

An integer overflow was addressed with improved input validation. This issue is fixed in macOS Sequoia 15.7.5, macOS Sonoma 14.8.5, macOS Tahoe 26.3. Processing a maliciously crafted string may lead to heap corruption.

Impact

The primary impact of CVE-2026-20639 is on system availability, as heap corruption can cause application or system crashes, leading to denial of service conditions. While the vulnerability does not directly compromise confidentiality or integrity, heap corruption can sometimes be leveraged in complex attack chains to execute arbitrary code or escalate privileges. Given the vulnerability can be exploited remotely without authentication or user interaction, it poses a significant risk to exposed macOS systems, especially those running vulnerable versions in network-facing roles. Organizations relying heavily on macOS for critical operations could face service disruptions, impacting business continuity. Additionally, the presence of this vulnerability increases the attack surface for threat actors targeting Apple environments. The lack of known exploits currently reduces immediate risk but does not eliminate the potential for future exploitation, especially as threat actors develop proof-of-concept code.

CWE-190Integer Overflow or Wraparound (opens in a new tab)
Base weaknessLikelihood of exploit: Medium
The product performs a calculation that can produce an integer overflow or wraparound when the logic assumes that the resulting value will always be larger than the original value. This occurs when an integer value is incremented to a value that is too large to store in the associated representation. When this occurs, the value may become a very small or negative number.
Requirements
Ensure that all protocols are strictly defined, such that all out-of-bounds behavior can be identified simply, and require strict conformance to the protocol.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
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
XML Security (opens in a new tab)
Mass Assignment (opens in a new tab)
OWASP ASVS 4.0.3
V5.4.3 (opens in a new tab)
V13.3.1 (opens in a new tab)
V5.1.4 (opens in a new tab)
Attack patterns
Forced Integer Overflow (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 3 Apr 2026, 02:53 UTC

WeaknessesCWE-190

Technical details

References

Community reviews

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