CVE-2021-25261
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedLocal privilege vulnerability in Yandex Browser for Windows prior to 22.5.0.862 allows a local, low privileged, attacker to execute arbitary code with the SYSTEM privileges through manipulating symlinks to installation file during Yandex Browser update process.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceThis is a local privilege escalation vulnerability in Yandex Browser's Windows update mechanism. A low-privileged local attacker can manipulate symlinks pointing to installation files during the update process to inject and execute arbitrary code with SYSTEM-level privileges. The vulnerability stems from the update process following untrusted symbolic links without proper validation.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data< 22.5.0.862CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Local
- Complexity
- Low
- Privileges
- Low
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:L/AC:L/PR:L/UI:N/S:U/C:H/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Verify Yandex Browser is installed on WindowsOpen File Explorer and navigate to C:\Users\[YourUsername]\AppData\Local\Yandex\YandexBrowser\Application, or check Program Files for Yandex folder. Alternatively, look for Yandex Browser in Start Menu.Affected if Yandex Browser executable (browser.exe) exists in these locations
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Determine installed Yandex Browser versionRight-click on browser.exe, select Properties, then go to the Details tab to view the Product Version. Or open the browser and navigate to about:yandex to see the version number.Affected if Version number displayed is lower than 22.5.0.862
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Confirm update component is presentNavigate to the update folder: C:\Users\[Username]\AppData\Local\Yandex\YandexBrowser\Update or C:\Program Files\Yandex\YandexBrowser\Update. Check for existence of update-related executables or configuration files.Affected if Update folder and files exist on the system
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Check write permissions on update directoriesRight-click the Yandex Browser installation and Update folders, select Properties, go to Security tab. Review which users or groups have Write or Modify permissions on these directories.Affected if Low-privileged users or groups (non-admin) have Write or Modify access to update folders
A system is affected if Yandex Browser version is below 22.5.0.862 AND the update mechanism is present AND unprivileged users can write to update-related directories to manipulate symlinks.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped22.5.0.862
Upgrade Yandex Browser for Windows to version 22.5.0.862 or later. Until patched, restrict write access to the browser's installation directories and update folders to prevent symlink manipulation by unprivileged users.
22.5.0.862 or later
- Open Yandex Browser and navigate to the browser settings menu
- Go to 'About Yandex Browser' or use the browser's built-in update check feature
- The browser will automatically check for and install updates
- Alternatively, download the latest version from the official Yandex website at yandex.com
- Ensure the installed version is 22.5.0.862 or later
Generated from the published advisory — verify against the referenced sources before acting.
- Consultation6.0 h
- Implementation12.0 h
- Testing6.0 h
- Review / QA4.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2021-25261 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2021-25261 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data