dbcve.org
FedoraOperating system · Fedoraproject

CVE-2020-6096

HIGH · 8.1 CVSS v3.1 Published 2020-04-01
Fix available
A fix is available. Upgrade to after 2.31 or later.
See remediation →
90/100
Remediation priority · Urgent
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
An exploitable signed comparison vulnerability exists in the ARMv7 memcpy() implementation of GNU glibc 2.30.9000. Calling memcpy() (on ARMv7 targets that utilize the GNU glibc implementation) with a negative value for the 'num' parameter results in a signed comparison vulnerability. If an attacker underflows the 'num' parameter to memcpy(), this vulnerability could lead to undefined behavior such as writing to out-of-bounds memory and potentially remote code execution. Furthermore, this memcpy() implementation allows for program execution to continue in scenarios where a segmentation fault or crash should have occurred. The dangers occur in that subsequent execution and iterations of this code will be executed with this corrupted data.

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

A signed comparison vulnerability exists in the ARMv7 memcpy() implementation of GNU glibc 2.30.9000. When the 'num' parameter is underflowed to a negative value, the signed comparison causes the function to mishandle buffer sizes, leading to out-of-bounds memory writes and potential remote code execution. The implementation incorrectly allows execution to continue where a crash should occur, propagating corrupted data.

MitigationUpgrade glibc to a patched version that uses unsigned comparison for the length parameter; additionally, validate all buffer length inputs in applications before calling memcpy to prevent passing negative values.

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
FedoraOperating system
Affected:= 31= 32
Debian LinuxOperating system
Affected:= 10.0
GlibcFramework / library
Affected:<= 2.31

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
High
Privileges
None
User interaction
None
Scope
Unchanged
Confidentiality
High
Integrity
High
Availability
High

CVSS:3.1/AV:N/AC:H/PR:N/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 checks

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

  1. Identify system architecture
    Run 'uname -m' or check /proc/cpuinfo for the processor architecture. The vulnerability specifically exists in the ARMv7 memcpy() implementation.
    Affected if The system is NOT running on ARMv7 (armv7l) architecture - the flaw only affects ARMv7 implementations of memcpy in glibc.
  2. Check installed glibc version
    Run 'ldd --version' or check the libc6 package version with 'rpm -q glibc' (Fedora) or 'dpkg -l libc6' (Debian).
    Affected if The installed glibc version is 2.31 or higher - versions above 2.31 contain the fix for the signed comparison issue.
  3. Verify glibc source version
    Check the glibc source code version if accessible, looking for the memcpy implementation in 'sysdeps/arm/armv7/memcpy.S' or similar ARMv7-specific memcpy files.
    Affected if The memcpy implementation uses signed comparison for the 'num' parameter instead of unsigned comparison - this indicates the vulnerable code is present.
  4. Confirm application usage of memcpy
    Review application code or binaries that call memcpy() and may pass length parameters that could underflow to negative values due to integer handling bugs.
    Affected if Applications call memcpy with length values that could become negative through integer underflow, allowing the signed comparison vulnerability to be triggered.

A system is affected if it runs on ARMv7 architecture with glibc version 2.31 or lower AND applications can pass negative length values to memcpy, triggering the signed comparison flaw.

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 a release after 2.31
Interim mitigation

Upgrade glibc to a patched version that uses unsigned comparison for the length parameter; additionally, validate all buffer length inputs in applications before calling memcpy to prevent passing negative values.

Fix this in Fedora Scoped from the published advisory
  • Consultation6.0 h
  • Implementation12.0 h
  • Testing10.0 h
  • Review / QA4.0 h
32.0 hours of engineering $5,580
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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-2020-6096 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
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