CVE-2021-1879
XSS in Apple Iphone Os ≤ 12.5.2
Raw vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:NCVSS and EPSS are reproduced from their sources (NVD, FIRST EPSS). Risk Priority is our own derived reading, not an NVD score.
Summary
CVE-2021-1879 is a medium-severity Cross-site Scripting (CWE-79) vulnerability in Apple Iphone Os. Its CVSS base score is 6.1 (Medium).
Operationally, exploitation aligns with the MITRE ATT&CK technique Protocol or Service Impersonation (T1001.003); ranked in the top 6% of CVEs by exploit likelihood; CISA has added it to the Known Exploited Vulnerabilities catalog.
Deeper analysis AI-assisted summary
Synthesised by an AI model from the NVD description and linked references — a reading aid, not an authoritative source.
The vulnerability CVE-2021-1879 is a cross-site scripting flaw (CWE-79) caused by insufficient management of object lifetimes during web content processing. It affects Apple iOS prior to versions 12.5.2 and 14.4.2, iPadOS prior to 14.4.2, and watchOS prior to 7.3.3, with a CVSS score of 6.1 reflecting network attack vector, low complexity, required user interaction, and scoped confidentiality and integrity impacts.
An attacker can exploit the issue by serving maliciously crafted web content that triggers universal cross-site scripting, allowing limited reading or modification of data across security boundaries on the affected device. The attack requires no authentication and can be delivered remotely, though user interaction such as visiting a web page is needed.
Apple security advisories for iOS 12.5.2, iOS 14.4.2, iPadOS 14.4.2, and watchOS 7.3.3 state that the issue is resolved by the improved object lifetime handling in those updates. The vendor notes awareness of reports indicating the vulnerability has been actively exploited in the wild.
OWASP Top 10 for Web (2025)
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2021-7343
Vulnerability Data
This issue was addressed by improved management of object lifetimes. This issue is fixed in iOS 12.5.2, iOS 14.4.2 and iPadOS 14.4.2, watchOS 7.3.3. Processing maliciously crafted web content may lead to universal cross site scripting. Apple is aware of…
more
a report that this issue may have been actively exploited..
- CWE(s)
- KEV Date Added
- 03 November 2021
Related Threats
MITRE ATT&CK Enterprise Techniques
CVEs Like This One
Affected Assets
Mitigating Controls
Control response
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V1.1.2V1.3.2
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.
Penetration testing submits XSS payloads to web applications, detecting cross-site scripting flaws for subsequent remediation.
Validates web inputs to reject script-related content that could produce XSS.
Output validation against expected content can reject or sanitize script content in generated web pages, reducing XSS exploitability.
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.
Secure SDLC practices directly target introduction of XSS via coding standards/testing (mostly), yet the single broad outcome leaves many specific neutralization vectors unaddressed (partial).
Patching and EOL replacement can remediate known XSS instances in libraries or frameworks (partial) but do nothing to enforce input neutralization in application code (none).
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.5.6 only promotes membership in groups to improve knowledge, receive alerts, and share information; it performs no action that stops XSS exploitation (or even the underlying neutralization defect) and is a pure dependency for other controls per the owner's labeling rule.