Security readout for executives and security teams
Plain-English summary
This Chrome flaw let a malicious website bypass some browser navigation restrictions using an iframe. It required user interaction but no account access. Google fixed it in Chrome 91.0.4472.77, and CISA lists it as known exploited, so any legacy or unmanaged Chrome installations should be treated as urgent cleanup.
Executive priority
Prioritize this above ordinary medium browser bugs because CISA lists it as exploited. The business risk is mainly unmanaged or obsolete browsers allowing web-based integrity impact after user interaction. Focus on proving browser update coverage, not deep exploit investigation.
Technical view
CVE-2021-30533 is CWE-863 insufficient policy enforcement in Chrome PopupBlocker before 91.0.4472.77. A remote attacker could use a crafted iframe to bypass navigation restrictions. CVSS 3.1 is 6.5 with network attack vector, low complexity, no privileges, user interaction required, and high integrity impact.
Likely exposure
Exposure is most likely on endpoints running Chrome earlier than 91.0.4472.77, especially unmanaged desktops, stale golden images, or systems pinned to old browser packages. Fedora and Gentoo advisories indicate Linux package managers may also be relevant for validation.
Exploitation context
CISA KEV listing supports known exploitation. The provided sources do not describe exploit volume, targets, or technical exploitation details. Treat this as a browser client-side risk where successful exploitation depends on a user reaching attacker-controlled content.
Researcher notes
Public details are limited in the provided bundle. The vulnerability is framed as PopupBlocker policy enforcement failure enabling navigation restriction bypass through iframe content. Avoid assuming code execution or data theft because the CVSS vector reports no confidentiality or availability impact.
Mitigation direction
- Upgrade Chrome to 91.0.4472.77 or later.
- Prioritize remediation under CISA KEV tracking.
- Remove or isolate unsupported legacy Chrome installations.
- Apply relevant Fedora or Gentoo browser package updates.
- Check current Google and distribution vendor guidance.
Validation and detection
- Inventory Chrome versions across managed endpoints.
- Confirm no installation is older than 91.0.4472.77.
- Review patch tooling for failed or pinned browser updates.
- Check Linux package advisory status where applicable.
- Record KEV remediation evidence for compliance tracking.
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-863: Authorization and privilege behavior lookup
Authorization weaknesses can support privilege escalation and valid-account review, depending on exploit path. 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-2021-30533 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
- 6.5 (3.1)
- Known Exploited
- Yes
- Published
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/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:U/C:N/I:H/A:N2.83.6Primary CVE scoreVulnerability scoring details
Base CVSS 3.1 score
6.5MediumVector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N
Source materials
- CVE List V5 sourceCVE List V5
- https://chromereleases.googleblog.com/2021/05/stable-channel-update-for-desktop_25.htmlCVE reference · x_refsource_MISC
- https://crbug.com/1145553CVE reference · x_refsource_MISC
- GLSA-202107-06CVE reference · vendor-advisory, x_refsource_GENTOO
- FEDORA-2021-f94dadff78CVE reference · vendor-advisory, x_refsource_FEDORA
- FEDORA-2021-ca58c57bdfCVE reference · vendor-advisory, x_refsource_FEDORA
- https://www.cisa.gov/known-exploited-vulnerabilities-catalog?field_cve=CVE-2021-30533CVE 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.
Incorrect Authorization
Incorrect Authorization represents a recurring weakness pattern that can create exploitable paths when design, validation, or implementation controls are missing.