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FedoraOperating system · Fedoraproject

CVE-2021-36976

MEDIUM · 6.5 CVSS v3.1 Published 2021-07-20
Fix available
A fix is available. Upgrade to 8.2.12 / 8.5 or later.
See remediation →
72/100
Remediation priority · Elevated
Remotely reachable No privileges

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
libarchive 3.4.1 through 3.5.1 has a use-after-free in copy_string (called from do_uncompress_block and process_block).

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 · moderate confidence

A use-after-free vulnerability exists in libarchive versions 3.4.1 through 3.5.1 in the copy_string function, which is called by do_uncompress_block and process_block during archive decompression. This memory safety flaw occurs when the code frees a string buffer but then attempts to access it later, potentially leading to remote code execution or denial of service when processing specially crafted compressed archives.

MitigationUpgrade libarchive to version 3.5.2 or later. Until patched, avoid processing untrusted or compressed archive files with vulnerable libarchive versions.

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:= 35
LibarchiveApplication
Affected:>= 3.4.1, <= 3.5.2
IpadosOperating system
Affected:< 15.4
Iphone OsOperating system
Affected:< 15.4
macOSOperating system
Affected:< 12.3
WatchosOperating system
Affected:< 8.5
Universal ForwarderApplication
Affected:>= 8.2.0, < 8.2.12>= 9.0.0, < 9.0.6= 9.1.0

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
Required
Scope
Unchanged
Confidentiality
None
Integrity
None
Availability
High

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:N/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. Check installed libarchive version
    Run `libarchive --version` or check your system's package manager (e.g., `rpm -q libarchive` on RHEL/Fedora, `dpkg -l libarchive` on Debian/Ubuntu)
    Affected if The version is >= 3.4.1 and <= 3.5.2
  2. Check if any application links to vulnerable libarchive
    Run `ldd /path/to/application | grep libarchive` or use `objdump -p /path/to/application | grep libarchive` to see which binaries use libarchive
    Affected if A linked application uses a libarchive library version in the affected range
  3. Identify compressed archive processing capabilities
    Review application logs or documentation to confirm if the target environment decompresses archive files (especially .tgz, .tar.gz, .tar.bz2, .tar.xz, or other compressed formats)
    Affected if The environment processes compressed archives using libarchive in the affected version range
  4. For Apple devices, check operating system version
    On iOS/iPadOS check Settings > General > About > Version; on macOS check System Preferences > About; on watchOS check Settings > General > About
    Affected if iOS/iPadOS < 15.4, macOS < 12.3, or watchOS < 8.5 - these ship with vulnerable libarchive versions
  5. For Splunk Universal Forwarder, check installed version
    Run `$SPLUNK_HOME/bin/splunk version` or check the installed package version via system package manager
    Affected if Version is 8.2.0 to 8.2.11, 9.0.0 to 9.0.5, or 9.1.0 (these ship with vulnerable libarchive)
  6. For Fedora 35, check libarchive package
    Run `dnf list installed libarchive` to confirm the package and version installed
    Affected if libarchive package is installed on Fedora 35 (ships with vulnerable version)

You are affected if your system runs libarchive 3.4.1 through 3.5.2 (or an affected Apple/Splunk product version) AND processes compressed archive files using that library.

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 8.2.12 / 8.5 / 9.0.6 or later
Fixed in 8.2.128.59.0.6
Interim mitigation

Upgrade libarchive to version 3.5.2 or later. Until patched, avoid processing untrusted or compressed archive files with vulnerable libarchive versions.

Fix this in Fedora Scoped from the published advisory
  • Consultation2.0 h
  • Implementation4.0 h
  • Testing8.0 h
  • Review / QA4.0 h
18.0 hours of engineering $3,040
Get the upgrade done

An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $4,864.

Scan for this in your stack

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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-2021-36976 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