CISA KEV entry
CVE-2021-1879Apple iOS, iPadOS, and watchOS WebKit Cross-Site Scripting (XSS) Vulnerability
Apple iOS, iPadOS, and watchOS. Added to the CISA Known Exploited Vulnerabilities catalogue on 3 November 2021.
Data status: a source is stale
Last synced CISA catalogue version 2026.11.04 (released 4 November 2026) 1,768 entries Updated manually
- Date added
- 2021-11-03
- Federal due date
- 2021-11-17 14 days after it was added; passed at the sync of 2026-11-05
- Known ransomware use
- Unknown
- Forensic triage (BOD 26-04)
- No
- CVSS
- 6.1 Medium CVSS 3.1, scored by nvd@nist.gov
- EPSS
- 7.08% percentile 94.2, scored 2026-11-04
- CISA SSVC
- Exploitation active, automatable no, technical impact partial
- NVD status
- Analyzed published 2021-04-02, 215 days before the KEV listing
BOD 26-04 remediation window
With CISA's SSVC answers for this CVE (automatable: no, technical impact: partial), BOD 26-04 Table 1 gives 14 days on a publicly exposed asset (row 4) and 14 days on an asset that is not publicly exposed (row 12) S06. The catalogue due date, 14 days after the date added, was set before BOD 26-04 took effect on 10 June 2026 S06. The directive binds US federal civilian executive branch agencies only.
What CISA says
Short description
Apple iOS, iPadOS, and watchOS WebKit contain an unspecified vulnerability that allows for universal cross-site scripting (XSS) when processing maliciously crafted web content. This vulnerability could impact HTML parsers that use WebKit, including but not limited to Apple Safari and non-Apple products which rely on WebKit for HTML processing.
Required action
Apply updates per vendor instructions.
Notes
https://nvd.nist.gov/vuln/detail/CVE-2021-1879
CWE in the catalogue
CWE-79
Official links
- CISA KEV catalogue entry cisa.gov
- NVD record nvd.nist.gov
Vendor advisory and patch links
References NVD tags Vendor Advisory or Patch, exactly as NVD lists them.
- https://support.apple.com/en-us/HT212256 Release Notes, Vendor Advisory
- https://support.apple.com/en-us/HT212257 Release Notes, Vendor Advisory
- https://support.apple.com/en-us/HT212258 Release Notes, Vendor Advisory
Links in CISA's notes
NVD details
- CWE (NVD)
- CWE-79 by nvd@nist.gov
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N- CVSS versions in NVD
- V2, V31
- Last modified in NVD
- 2026-06-17T03:32:42.883
Where each value comes from
| Field | Source | Fetched, UTC | State |
|---|---|---|---|
| Catalogue fields | CISA KEV JSON, version 2026.11.04 | 2026-11-05 11:38 | current |
| NVD published, status, CVSS, CWE, vendor links | NVD CVE API 2.0; CVSS: NVD (nvd@nist.gov) | 2026-11-03 12:37 | current at 2026-11-05 11:38 |
| EPSS | FIRST EPSS API, scores of 2026-11-04 | 2026-11-05 11:38 | current |
| CISA SSVC | CISA ADP (via NVD), record of 2025-01-29 | 2026-11-03 12:37 | current |
This product uses data from the NVD API but is not endorsed or certified by the NVD. CISA does not endorse Sysprobs. Methodology.