Security readout for executives and security teams
Plain-English summary
CVE-2021-25263 is a Windows local privilege escalation issue in Yandex Browser before 21.9.0.390. A user with low privileges could potentially turn local access into SYSTEM-level code execution by abusing insecure file permissions during the browser update process.
Executive priority
Treat this as a high-priority endpoint hygiene issue if Yandex Browser is present. It is not described as remotely exploitable, but successful abuse could grant SYSTEM privileges on affected Windows machines after local access.
Technical view
The CVE describes insecure permissions in a directory used by the Yandex Browser update process on Windows. A local, low-privileged attacker could manipulate files there and cause arbitrary code execution with SYSTEM privileges. The source bundle does not provide CVSS, CWE, or detailed exploit mechanics.
Likely exposure
Exposure is limited to Windows endpoints running Yandex Browser Desktop versions earlier than 21.9.0.390. Risk is most relevant on shared workstations, developer systems, kiosks, or compromised user accounts where a local attacker can interact with the update path.
Exploitation context
The source bundle does not show CISA KEV listing or any cited confirmation of active exploitation. The issue requires local low-privileged access, so it is more likely used after initial compromise than as an internet-facing entry point.
Researcher notes
Evidence is limited to the CVE description and affected version statement. No CVSS, CWE, exploit status, or deep technical advisory is included. Avoid assuming affected update components beyond the described insecure-permission update-process directory behavior.
Mitigation direction
- Upgrade Yandex Browser for Windows to 21.9.0.390 or later where installed.
- Check Yandex Browser vendor guidance for current remediation details.
- Remove Yandex Browser from endpoints where it is not business-required.
- Use endpoint controls to restrict untrusted local code execution.
- Prioritize remediation on shared or high-value Windows systems.
Validation and detection
- Inventory Windows endpoints for Yandex Browser Desktop installations.
- Confirm installed versions are 21.9.0.390 or later.
- Review software deployment records for outdated Yandex Browser packages.
- Check endpoint management tools for unmanaged browser installations.
- Document exceptions and monitor them until remediated.
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.
CVE-2021-25263 mapping review
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Open ATT&CK lookup- Severity
- Unknown
- CVSS
- Not scored
- Known Exploited
- No
- Published
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.
CVSS and timeline data
No CVSS vectors or timeline events were available in the normalized CVE source material.
Source materials
- CVE List V5 sourceCVE List V5
- https://yandex.com/bugbounty/i/hall-of-fame-browser/CVE reference · x_refsource_MISC
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.