CVE-2020-9819
Apple iOS, iPadOS, and watchOS Memory Corruption Vulnerability
Description
CVE-2020-9819 is a medium-severity memory corruption vulnerability in Apple iOS, iPadOS, and watchOS Mail. The flaw allows a maliciously crafted mail message to cause heap corruption when processed by the Mail application. CISA has added this vulnerability to its Known Exploited Vulnerabilities (KEV) catalog, confirming active exploitation in the wild. With an EPSS score of 0.20% (41.6th percentile), CVE-2020-9819 poses a notable risk particularly when chained with other vulnerabilities such as CVE-2020-9818 for greater impact.
KEV Information
CVSS Score
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:LOpen in CalculatorAffected Products
| Vendor | Product | Version |
|---|---|---|
| apple | ipados | < 13.5 |
| apple | iphone os | < 12.4.7; >= 13.0, < 13.5 |
| apple | watchos | < 5.3.7; >= 6.0.0, < 6.2.5 |
Multiple CVSS Assessments
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L
References
- https://support.apple.com/HT211168(Release Notes, Vendor Advisory)
- https://support.apple.com/HT211169(Release Notes, Vendor Advisory)
- https://support.apple.com/HT211175(Release Notes, Vendor Advisory)
- https://support.apple.com/HT211176(Release Notes, Vendor Advisory)
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2020-9819(US Government Resource)
Weakness Type
CWE-787: Out-of-bounds Write
Out-of-bounds write is a vulnerability class where software writes data beyond the intended boundaries of a buffer. In CVE-2020-9819, improper memory handling in the Apple Mail application leads to heap corruption when processing malicious email content, allowing memory consumption issues that can destabilize the application.
Learn more: CWE-787 — Out-of-bounds Write
Impact Analysis
CVE-2020-9819 carries a CVSS 3.1 score of 4.3 (MEDIUM), indicating a moderate threat. The vulnerability is remotely exploitable over the network with low attack complexity and requires no authentication, though user interaction is needed. The impact is limited to availability, with low impact on system availability and no direct effect on confidentiality or integrity. However, this vulnerability is significant because it has been exploited in the wild, and heap corruption can serve as a building block for more sophisticated attacks when combined with other vulnerabilities targeting the same application.
Exploit Maturity
CVE-2020-9819 is confirmed as actively exploited through its inclusion in the CISA Known Exploited Vulnerabilities catalog. The EPSS score of 0.20% (41.6th percentile) indicates a relatively low individual exploitation probability, but the confirmed active exploitation status suggests this vulnerability has been used in targeted attack campaigns, likely in combination with CVE-2020-9818 which targets the same Apple Mail component. No public exploit code was identified in the available references. Federal agencies were required to remediate this vulnerability by 2022-05-03 per CISA's binding operational directive.
Remediation
- Apply vendor patches immediately as mandated by CISA KEV: Apply updates per vendor instructions. Update to iOS 13.5/iPadOS 13.5, iOS 12.4.7, watchOS 6.2.5, or watchOS 5.3.7.
- Verify that all Apple devices running affected software versions have been updated: iPhone OS (< 12.4.7; >= 13.0, < 13.5), iPadOS (< 13.5), and watchOS (< 5.3.7; >= 6.0.0, < 6.2.5).
- As an interim measure, disable automatic mail fetching and restrict the processing of untrusted email content to reduce exposure to maliciously crafted messages.
- Monitor Mail application behavior for signs of heap corruption, including unexpected memory consumption spikes, application crashes, or unusual process restarts.
- Deploy email security solutions at the network gateway to scan and filter incoming messages for characteristics associated with exploitation of mail processing vulnerabilities.
Technical Details
CVE-2020-9819 is a memory consumption vulnerability in the Apple Mail application that leads to heap corruption. The flaw resides in how the Mail app handles memory during message processing. According to the CVSS vector (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/A:L), the vulnerability is network-accessible with low complexity and requires no privileges but needs user interaction. The scope is unchanged, and the impact is limited to low availability disruption with no confidentiality or integrity impact. When a maliciously crafted email is processed, the application fails to properly manage memory allocation, resulting in heap corruption. Apple addressed this issue with improved memory handling across iOS 13.5, iPadOS 13.5, iOS 12.4.7, watchOS 6.2.5, and watchOS 5.3.7.
Frequently Asked Questions
Is CVE-2020-9819 being actively exploited?
Yes. CVE-2020-9819 is listed in the CISA Known Exploited Vulnerabilities catalog, confirming active exploitation in the wild. It has been observed in targeted attacks, likely in combination with CVE-2020-9818 for greater impact.
What products are affected by CVE-2020-9819?
CVE-2020-9819 affects Apple iPadOS (< 13.5), iPhone OS (< 12.4.7; >= 13.0, < 13.5), and watchOS (< 5.3.7; >= 6.0.0, < 6.2.5). The vulnerability targets the Mail application on these platforms.
How do I fix CVE-2020-9819?
Apply updates per vendor instructions. Update affected devices to iOS 13.5, iPadOS 13.5, iOS 12.4.7, watchOS 6.2.5, or watchOS 5.3.7. If immediate patching is not feasible, disable automatic mail fetching and implement email gateway filtering.
How severe is CVE-2020-9819?
CVE-2020-9819 has a CVSS 3.1 score of 4.3 (MEDIUM). While the direct impact is limited to availability, the confirmed active exploitation and potential for chaining with other vulnerabilities like CVE-2020-9818 increase its overall risk significance.
Need Help With Vulnerability Management?
Our security experts can help you prioritize and remediate vulnerabilities effectively.