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Debian LinuxOperating system · Debian

CVE-2021-25634

HIGH · 7.5 CVSS v3.1 Published 2021-10-12
Fix available
A fix is available. Upgrade to 7.0.6 / 7.1.2 or later.
See remediation →
84/100
Remediation priority · High
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
LibreOffice supports digital signatures of ODF documents and macros within documents, presenting visual aids that no alteration of the document occurred since the last signing and that the signature is valid. An Improper Certificate Validation vulnerability in LibreOffice allowed an attacker to modify a digitally signed ODF document to insert an additional signing time timestamp which LibreOffice would incorrectly present as a valid signature signed at the bogus signing time. This issue affects: The Document Foundation LibreOffice 7-0 versions prior to 7.0.6; 7-1 versions prior to 7.1.2.

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

LibreOffice has an improper certificate validation vulnerability in its digital signature handling for ODF documents. An attacker can modify a signed document to insert a bogus signing time timestamp, which LibreOffice will incorrectly validate and present as a legitimate signature timestamp, undermining the integrity of digitally signed documents.

MitigationUpgrade LibreOffice to version 7.0.6 or later (for 7-0 branch) or 7.1.2 or later (for 7-1 branch). Verify that digital signature functionality works correctly after the upgrade.

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:= 11.0
LibreofficeApplication
Affected:>= 7.0.0, < 7.0.6>= 7.1.0, < 7.1.2

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
High
Availability
None

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

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 the installed LibreOffice version
    Open LibreOffice, go to Help > About LibreOffice. Alternatively, run 'libreoffice --version' from command line. On Debian, also check with 'dpkg -l | grep libreoffice'
    Affected if The version is 7.0.0 through 7.0.5.x, or 7.1.0 through 7.1.1.x
  2. Verify the document-signing module is in use
    Check if users work with signed ODF documents (.odt, .ods, .odp files) by reviewing recent file access or asking users about digital signature workflows
    Affected if Signed ODF documents are processed and the LibreOffice version falls within the affected range
  3. Inspect signature validation behavior
    Open a signed ODF document in LibreOffice, right-click the signature, and check the signature panel. Look for the timestamp displayed. Compare it against the actual signature certificate properties
    Affected if A timestamp is shown in the signature details but the version is in the vulnerable range, indicating incorrect timestamp validation may be occurring

You are affected if LibreOffice version is 7.0.0-7.0.5 or 7.1.0-7.1.1 and you validate digital signatures on ODF documents.

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.

dbcve · scoped
Upgrade available Upgrade to 7.0.6 / 7.1.2 or later
Fixed in 7.0.67.1.2
Interim mitigation

Upgrade LibreOffice to version 7.0.6 or later (for 7-0 branch) or 7.1.2 or later (for 7-1 branch). Verify that digital signature functionality works correctly after the upgrade.

Recommended fix High confidence

LibreOffice 7.0.6 or later in the 7.0.x series; LibreOffice 7.1.2 or later in the 7.1.x series

  1. For Debian Linux 11.0: Run 'apt update' followed by 'apt install --only-upgrade libreoffice' to upgrade to the patched version available in Debian repositories
  2. For other Linux distributions: Use your distribution's package manager to update LibreOffice (e.g., 'sudo apt-get update && sudo apt-get upgrade libreoffice' on Ubuntu)
  3. Alternatively, download LibreOffice 7.0.6 or later (or 7.1.2 or later) from the official LibreOffice website and install manually
  4. After upgrade, verify the installed version by opening LibreOffice and going to Help > About LibreOffice, or run 'libreoffice --version' from command line
  5. Ensure the version shown is 7.0.6 or later in the 7.0.x series, or 7.1.2 or later in the 7.1.x series
Caveat Minor version upgrades typically have no breaking changes; however, some UI or feature changes may occur between 7.0.x and 7.1.x branches

Generated from the published advisory — verify against the referenced sources before acting.

Fix this in Debian Linux Scoped from the published advisory
  • Consultation2.0 h
  • Implementation2.0 h
  • Testing2.0 h
  • Review / QA1.0 h
7.0 hours of engineering $1,240
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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-2021-25634 in production — separate from our analysis above.

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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