CVE-2021-25633 Content Manipulation with Double Certificate Attack

What is CVE-2021-25633?

CVE-2021-25633 is a high-severity vulnerability in Debian Debian Linux, published on 11 Oct 2021. An attacker can exploit it over the internet without logging in, with no action from the victim.

Official description

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.

Weakness: CWE-295

Which versions are affected by CVE-2021-25633?

It affects 2 products.

Products include Debian Debian Linux, Libreoffice Libreoffice.

How do I fix CVE-2021-25633?

Upgrade to a fixed version.

Is CVE-2021-25633 being exploited?

There is no known exploitation of CVE-2021-25633 in the wild and no public exploit code.

Other vulnerabilities in Debian Debian Linux

• CVE-2015-3306 ProFTPD Improper Access Control Exploited Critical 10.0
• CVE-2025-49113 RoundCube Webmail Deserialization of Untrusted Data Exploited Critical 9.9
• CVE-2026-24061 GNU InetUtils Argument Injection Exploited Critical 9.8
• CVE-2025-39682 Linux Kernel Improper Check for Unusual or Exceptional Conditions Exploited Critical 9.8
• CVE-2024-9680 Mozilla Firefox Use-After-Free Exploited Critical 9.8

All Debian Debian Linux vulnerabilities

Sources

• CVE record
• NVD
• OSV
• GitHub advisory
• How this page is made

Also known as DEBIAN-CVE-2021-25633, GHSA-fx8r-3hmx-c78j, UBUNTU-CVE-2021-25633.