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Debian LinuxOperating system · Debian

CVE-2021-25633

HIGH · 7.5 CVSS v3.1 Published 2021-10-11
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 create a digitally signed ODF document, by manipulating the documentsignatures.xml or macrosignatures.xml stream within the document to combine multiple certificate data, which when opened caused LibreOffice to display a validly signed indicator but whose content was unrelated to the signature shown. 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

Improper certificate validation in LibreOffice allows attackers to manipulate the documentsignatures.xml or macrosignatures.xml streams within ODF documents to combine multiple certificate data. This causes LibreOffice to display a validly signed indicator while the document content is actually unrelated to the signature shown, bypassing the trust model for digital signatures.

MitigationUpgrade to LibreOffice 7.0.6 or later (7-0 series) or 7.1.2 or later (7-1 series) which contain the fix for proper certificate validation in signature stream parsing.

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. Check installed LibreOffice version
    Open LibreOffice, go to Help > About LibreOffice (or on Linux run: libreoffice --version or apt list --installed libreoffice*)
    Affected if The version is 7.0.0 to 7.0.5, or 7.1.0 to 7.1.1 (including any point releases within these ranges)
  2. Identify signed ODF documents
    Inspect ODF files (odt, ods, odp) by checking for META-INF/documentsignatures.xml or META-INF/macrosignatures.xml files inside the document archive
    Affected if The environment contains ODF documents with existing digital signatures in the META-INF folder
  3. Verify signature covers document content
    Open the signed document in LibreOffice, go to File > Digital Signatures and compare the listed certificates against the actual document revision history and content hashes
    Affected if The signature shows as valid but the certificate used does not correspond to the document author or the content was modified after signing
  4. Check for certificate stream manipulation
    Extract and examine documentsignatures.xml or macrosignatures.xml from signed ODF files - look for multiple certificate references or mismatched signer information within the same signature element
    Affected if The XML contains combined certificate data from different sources or displays inconsistent signer identities

You are affected if you run a vulnerable LibreOffice version (7.0.0-7.0.5 or 7.1.0-7.1.1) AND have ODF documents with digital signatures that may show valid but actually bind incorrect certificates to document content.

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 to LibreOffice 7.0.6 or later (7-0 series) or 7.1.2 or later (7-1 series) which contain the fix for proper certificate validation in signature stream parsing.

Recommended fix High confidence

LibreOffice 7.0.6 for 7.0.x branch, LibreOffice 7.1.2 for 7.1.x branch, or latest stable release (7.2.x or newer)

  1. Check current LibreOffice version by running: libreoffice --version or apt list --installed | grep libreoffice
  2. For Debian Linux 11.0 systems, update package lists: sudo apt-get update
  3. Upgrade LibreOffice to the fixed version: sudo apt-get upgrade libreoffice
  4. Alternatively, download LibreOffice 7.0.6 or 7.1.2 (or newer stable) from the official website: https://www.libreoffice.org/download/download/
  5. Verify the upgrade was successful by checking: libreoffice --version
Caveat Minimal risk; minor UI or macro compatibility changes possible between major minor versions

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

Fix this in Debian Linux Scoped from the published advisory
  • Consultation8.0 h
  • Implementation24.0 h
  • Testing16.0 h
  • Review / QA8.0 h
56.0 hours of engineering $9,760
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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-2021-25633 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