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Debian LinuxOperating system · Debian

CVE-2020-8927

MEDIUM · 6.5 CVSS v3.1 Published 2020-09-15
Fix available
A fix is available. Upgrade to 1.0.8 / 7.0.9 or later.
See remediation →
74/100
Remediation priority · Elevated
Remotely reachable No privileges Zero-click

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 · unedited
A buffer overflow exists in the Brotli library versions prior to 1.0.8 where an attacker controlling the input length of a "one-shot" decompression request to a script can trigger a crash, which happens when copying over chunks of data larger than 2 GiB. It is recommended to update your Brotli library to 1.0.8 or later. If one cannot update, we recommend to use the "streaming" API as opposed to the "one-shot" API, and impose chunk size limits.

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 confidence

Buffer overflow in Brotli library versions prior to 1.0.8 where an attacker controlling the input length of a 'one-shot' decompression request can trigger a crash by providing data that causes chunks larger than 2 GiB to be copied during decompression.

MitigationUpdate Brotli library to version 1.0.8 or later; alternatively, refactor code to use the streaming API instead of one-shot API with enforced chunk size limits.

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
Debian LinuxOperating system
Affected:= 9.0= 10.0
FedoraOperating system
Affected:= 31= 32= 33= 34= 35= 36
Ubuntu LinuxOperating system
Affected:= 16.04= 18.04= 20.04
BrotliApplication
Affected:< 1.0.8
LeapOperating system
Affected:= 15.2
.netApplication
Affected:>= 5.0, <= 5.0.14
.net CoreApplication
Affected:>= 3.1, <= 3.1.22
PowershellApplication
Affected:>= 7.0, < 7.0.9>= 7.1, < 7.1.6>= 7.2, < 7.2.2

CVSS 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
Network
Complexity
Low
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
None
Integrity
Low
Availability
Low

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L

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 checks

Work through these to decide whether this CVE applies to you.

  1. Identify installed Brotli library version
    Run 'brotli --version' or check package manager: 'dpkg -l | grep brotli' (Debian/Ubuntu), 'rpm -qa | grep brotli' (Fedora), or inspect the shared library file for version info
    Affected if Version is lower than 1.0.8 (e.g., 1.0.7, 1.0.6, etc.)
  2. Identify PowerShell version
    Run 'pwsh --version' or 'powershell -Command $PSVersionTable.PSVersion'
    Affected if Version is 7.0.x below 7.0.9, 7.1.x below 7.1.6, or 7.2.x below 7.2.2
  3. Identify .NET runtime version
    Run 'dotnet --list-runtimes' to see installed .NET Core/5+ runtimes, or check registry on Windows for installed versions
    Affected if .NET 5.0.x at or below 5.0.14, or .NET Core 3.1.x at or below 3.1.22 is installed
  4. Verify one-shot decompression API usage
    Search codebase for calls to BrotliDecoder.Decode or similar one-shot decompression functions (non-streaming) that accept user-supplied input length parameters
    Affected if Code uses the one-shot (non-streaming) decompression API where an attacker can control the input length
  5. Check for large input handling
    Review if decompression logic processes input that could result in chunks exceeding 2 GiB during decompression
    Affected if Application decompresses untrusted Brotli-compressed data without chunk size limits

You are affected if you have a vulnerable Brotli library version (<1.0.8), vulnerable .NET/PowerShell version, AND your code uses the one-shot decompression API with attacker-controlled input that could produce decompressed chunks larger than 2 GiB.

Generated from the published advisory. Verify against your own configuration.

Check your environment

Paste your version and any relevant configuration and it will be compared against the affected criteria above. Do not include secrets or credentials.

AI-assisted, checked against the advisory. Informational, not a guarantee.

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.

From vendor data
Upgrade available Upgrade to 1.0.8 / 7.0.9 / 7.1.6 or later
Fixed in 1.0.87.0.97.1.6
Interim mitigation

Update Brotli library to version 1.0.8 or later; alternatively, refactor code to use the streaming API instead of one-shot API with enforced chunk size limits.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing2.0 h
  • Review / QA1.0 h
9.0 hours of engineering $1,600
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References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.

Primary sources

Practitioner notes

Contributed

Peer-ranked notes from engineers who’ve handled CVE-2020-8927 in production — separate from our analysis above.

No notes yet

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What this is

A place for practitioners to share what actually worked: a mitigation you’ve tested, a configuration change, a version- or environment-specific caveat, or a link to a verified patch. The most useful notes rise to the top as peers upvote them, so the signal stays high.

What belongs here
  • 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