Cyber Resilience

CVE-2020-27930

Memory Safety in Apple Watchos ≤ 5.3.9

CISA KEVActive ExploitationEUVD ExploitedPublic PoCMemory Safety
Published
08 December 2020
Modified
27 October 2025
KEV Added
03 November 2021
Patch / advisory
View advisory
CVSS Score v3.1 7.8
Click a component to see what it means
Raw vectorCVSS:3.1/AV:L/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
EPSS Score 0.22 97th percentile
Risk Priority 83 floored blend · peak EPSS

Summary

CVE-2020-27930 is a high-severity Out-of-bounds Write (CWE-787) vulnerability in Apple Watchos. Its CVSS base score is 7.8 (High).

Operationally, exploitation aligns with the MITRE ATT&CK technique Exploitation for Privilege Escalation (T1068); ranked in the top 3% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog; a public proof-of-concept is referenced.

Deeper analysis AI-assisted summary

Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.

A memory corruption vulnerability addressed through improved input validation affects font processing across multiple Apple platforms. The issue impacts macOS versions prior to Big Sur 11.0.1, Catalina 10.15.7 Supplemental Update, and Security Update 2020-006 for High Sierra and Mojave; iOS and iPadOS prior to 14.2 and 12.4.9; and watchOS prior to 7.1, 6.2.9, and 5.3.9. It is tracked as CWE-787 with a CVSS score of 7.8.

An attacker can trigger the flaw by supplying a maliciously crafted font file that the victim processes locally, such as by viewing a document or web page containing the font. Successful exploitation grants arbitrary code execution with the privileges of the affected process, though it requires user interaction to open the crafted content.

Apple security advisories for the listed updates, including HT211928, HT211929, and HT211931, direct users to install the available patches. Public references also include exploit artifacts posted to Packet Storm and Full Disclosure lists shortly after publication.

The references indicate at least one proof-of-concept targeting Safari via this vector, though no widespread in-the-wild exploitation is documented in the provided details.

EU & UK References

Vulnerability Data

A memory corruption issue was addressed with improved input validation. This issue is fixed in macOS Big Sur 11.0.1, watchOS 7.1, iOS 12.4.9, watchOS 6.2.9, Security Update 2020-006 High Sierra, Security Update 2020-006 Mojave, iOS 14.2 and iPadOS 14.2, watchOS…

more

5.3.9, macOS Catalina 10.15.7 Supplemental Update, macOS Catalina 10.15.7 Update. Processing a maliciously crafted font may lead to arbitrary code execution.

CWE(s)
CWE-787
KEV Date Added
03 November 2021

Related Threats

MITRE ATT&CK Enterprise Techniques

T1068 Exploitation for Privilege Escalation Privilege Escalation
Adversaries may exploit software vulnerabilities in an attempt to elevate privileges.
attack.mitre.org →
T1190 Exploit Public-Facing Application Initial Access
Adversaries may attempt to exploit a weakness in an Internet-facing host or system to initially access a network.
attack.mitre.org →
T1203 Exploitation for Client Execution Execution
Adversaries may exploit software vulnerabilities in client applications to execute code.
attack.mitre.org →
T1210 Exploitation of Remote Services Lateral Movement
Adversaries may exploit remote services to gain unauthorized access to internal systems once inside of a network.
attack.mitre.org →
T1211 Exploitation for Stealth Stealth
Adversaries may exploit vulnerabilities to evade detection by hiding activity, suppressing logging, or operating within trusted or unmonitored components.
attack.mitre.org →
T1212 Exploitation for Credential Access Credential Access
Adversaries may exploit software vulnerabilities in an attempt to collect credentials.
attack.mitre.org →
Derived from this CVE’s CWE(s) via the direct CWE→ATT&CK cross-walk.

CVEs Like This One

CVE-2022-32894Same product: Apple Ipadosboth on KEV
CVE-2021-30807Same product: Apple Ipadosboth on KEV
CVE-2022-22675Same product: Apple Ipadosboth on KEV
CVE-2021-30665Same product: Apple Ipadosboth on KEV
CVE-2021-30883Same product: Apple Ipadosboth on KEV
CVE-2020-3837Same product: Apple Ipadosboth on KEV
CVE-2022-22587Same product: Apple Ipadosboth on KEV
CVE-2023-28206Same product: Apple Ipadosboth on KEV
CVE-2020-9818Same product: Apple Ipadosboth on KEV
CVE-2022-32917Same product: Apple Ipadosboth on KEV

Affected Assets

apple
ipados
≤ 14.2
apple
iphone os
≤ 12.4.9 · 14.0 — 14.2
apple
mac os x
≤ 10.15.7
apple
macos
11.0 — 11.0.1
apple
watchos
≤ 5.3.9 · 6.0 — 6.2.9 · 7.0 — 7.1

Mitigating Controls

Likely Mitigating Controls AI

Per-CVE control mapping for this CVE has not run yet; the list below is derived from the weakness types (CWEs) cited in the NVD entry.

SI-16 Memory Protection
addresses: CWE-787

Out-of-bounds writes that corrupt control flow or inject shellcode are rendered non-executable by the same memory protections.

Mitigating Controls (NIST CSF 2.0) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→CSF cross-walk (authority under review) — links open the control.

PR.PS-06 mostly match
prevents

Secure-development practices (static analysis, bounds checking, code review) are the primary means of preventing out-of-bounds writes.

ID.RA-01 partial match
prevents

Vulnerability scanning and recording can discover out-of-bounds write flaws so they can be remediated.

PR.PS-02 partial match
prevents

Patching or replacing vulnerable software directly eliminates known instances of this coding weakness.

Mitigating Controls (ISO/IEC 27001:2022 Annex A) AI

Derived directly from the weakness types (CWEs) cited in the NVD entry via our AI-authored CWE→ISO cross-walk (authority under review) — links open the control.

A.8.29 Security testing in development and acceptance mostly match
finds

Security testing in development and acceptance can detect and prevent out-of-bounds write defects.

A.8.25 Secure development life cycle partial match
prevents

Secure development life cycle mandates practices that prevent out-of-bounds writes.

A.8.26 Application security requirements partial match
prevents

Application security requirements can specify bounds-checking and safe memory handling.

A.8.27 Secure system architecture and engineering principles partial match
prevents

Secure architecture and engineering principles reduce the likelihood of buffer overflows.

A.8.28 Secure coding partial match
prevents

Secure coding directly addresses out-of-bounds writes through language choice and coding standards.

A.8.32 Change management partial match
prevents

Change management can enforce review gates that catch unsafe memory operations before deployment.

References