Security readout for executives and security teams
Plain-English summary
CVE-2021-1879 is an Apple web-content flaw that could let malicious web content perform universal cross-site scripting. The business concern is mobile device exposure: Apple reported possible active exploitation, and CISA lists it as known exploited. Devices should be verified at or beyond Apple’s fixed versions.
Executive priority
Treat this as a high-priority legacy Apple device exposure because it is in CISA KEV and Apple reported possible active exploitation. The immediate action is patch verification, not deep investigation, unless unpatched high-value devices are found.
Technical view
Apple describes an object-lifetime management issue leading to universal XSS when processing maliciously crafted web content. The CVSS 3.1 score is 6.1 with network attack vector, low complexity, no privileges, and required user interaction. Apple fixed it in iOS 12.5.2, iOS/iPadOS 14.4.2, and watchOS 7.3.3.
Likely exposure
Exposure is most likely on Apple mobile and watch devices below the fixed releases: iOS 12.5.2, iOS/iPadOS 14.4.2, or watchOS 7.3.3. The source data does not identify specific vulnerable model ranges or app components beyond processing maliciously crafted web content.
Exploitation context
Apple says it was aware of a report that the issue may have been actively exploited. CISA’s Known Exploited Vulnerabilities listing confirms exploitation relevance. Public source details do not identify campaigns, targets, exploit chains, or indicators.
Researcher notes
Evidence supports universal XSS from malicious web content and an object-lifetime fix, but public sources provide limited implementation detail. Do not infer affected browsers, exploit primitives, or exploit-chain role beyond Apple’s wording and CISA KEV status.
Mitigation direction
- Update affected iOS, iPadOS, and watchOS devices to Apple’s fixed versions or later.
- Use MDM or inventory tooling to enforce minimum supported Apple OS versions.
- Prioritize devices used by executives, administrators, and high-risk mobile users.
- Check Apple’s security guidance for any newer superseding update recommendations.
Validation and detection
- Inventory Apple iOS, iPadOS, and watchOS versions across managed and unmanaged devices.
- Confirm iOS 12 devices are at least 12.5.2 where still supported.
- Confirm iOS and iPadOS 14 devices are at least 14.4.2.
- Confirm watchOS devices are at least 7.3.3.
- Review exception lists for devices that cannot receive the fixed releases.
Public sources used
Generated from the cited source records. This long-tail analysis has not been individually reviewed by a named human.
Conservative CVE-to-ATT&CK context
These mappings and lookup hints may be relevant to the vulnerability behavior, CWE, affected product, or exposure path. Glexia-inferred context is not an official MITRE, ATT&CK, CWE, or CVE Program mapping.
ATT&CK lookup starting points
Use these exact CWE pages and searches to review the Glexia ATT&CK library from this CVE's weakness and description context.
CWE-79: User-session and phishing behavior lookup
Client-side and session-facing weaknesses should be reviewed alongside initial-access and user-execution behaviors. Open the exact CWE lookup page first, then review the ATT&CK searches from that MITRE weakness context. This is a Glexia lookup hint, not an official ATT&CK mapping.
Open ATT&CK lookupCVE-2021-1879 mapping review
Open the CVE-to-ATT&CK bridge for reviewed, inferred, or future official mappings tied to this CVE.
Open ATT&CK lookup- Severity
- Medium
- CVSS
- 6.1 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
CNA and ADP enrichment extracted from CVE v5
These fields come from the CVE record and ADP containers, not from Glexia's Take. They preserve time-varying source decisions such as CISA SSVC, KEV status, CVSS metrics, and provider references.
CISA KEV status
CVSS vector scores
1 official scoreWe collect every scored CVSS vector available in the official CNA and ADP containers. When more than one version is present, the table keeps the source vectors side by side instead of collapsing them into the highest score.
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N2.82.7Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.1MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://support.apple.com/en-us/HT212256CVE reference · x_refsource_MISC
- https://support.apple.com/en-us/HT212257CVE reference · x_refsource_MISC
- https://support.apple.com/en-us/HT212258CVE reference · x_refsource_MISC
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-1879CVE reference · government-resource
Products and packages named in the record
CWE details
CWE links open Glexia weakness intelligence pages with official CWE context, developer remediation guidance, and related CVE mappings.