Security readout for executives and security teams
Plain-English summary
This issue affects Yandex Browser for Windows before 22.5.0.862. A person who already has low-level local access to a machine could abuse the browser update process to run code as SYSTEM. That makes it a serious endpoint hardening issue, but the sources do not show internet-scale remote exploitation.
Executive priority
Treat this as high priority where Yandex Browser is present on Windows endpoints. It is not presented as remotely exploitable from the internet, but successful abuse could give an already-present attacker full SYSTEM control of the affected machine.
Technical view
CVE-2021-25261 is a local privilege escalation in Yandex Browser Desktop on Windows before 22.5.0.862. The CVE description attributes the flaw to symlink handling around installation files during the update process, allowing arbitrary code execution with SYSTEM privileges by a local low-privileged attacker.
Likely exposure
Exposure is limited to Windows endpoints running Yandex Browser Desktop versions earlier than 22.5.0.862. The source bundle does not identify affected server products, non-Windows platforms, or bundled enterprise management components.
Exploitation context
CISA KEV status is false, and the provided sources do not cite active exploitation or public exploit availability. The attack requires local low-privileged access first, so risk is highest on shared workstations, compromised endpoints, and environments with weak endpoint controls.
Researcher notes
The public record is sparse: no CVSS vector, CWE, detailed advisory, or exploit-status evidence is included. The core assessment rests on the CVE description and affected-version statement. Avoid assuming broader product impact beyond Yandex Browser Desktop on Windows before 22.5.0.862.
Mitigation direction
- Upgrade Yandex Browser for Windows to version 22.5.0.862 or later.
- Inventory managed endpoints for outdated Yandex Browser installations.
- Review Yandex vendor guidance for any additional update-process hardening advice.
- Restrict unnecessary local user access on shared Windows systems.
- Prioritize remediation on high-risk workstations and administrator jump hosts.
Validation and detection
- Confirm installed Yandex Browser versions are 22.5.0.862 or later.
- Check software inventory for Windows systems with older browser builds.
- Review endpoint telemetry for unusual SYSTEM-level activity tied to browser updates.
- Verify patch compliance after update deployment.
- Document any unsupported or unmanaged Yandex Browser installations.
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-2021-25261 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
- 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.