Document spoofing in LibreOffice

1) Improper certificate validation

EUVDB-ID: #VU60762

Risk: Low

CVSSv3.1: 3.8 [CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:L/A:N/E:U/RL:O/RC:C]

CVE-ID: CVE-2021-25636

CWE-ID: CWE-295 - Improper Certificate Validation

Exploit availability: No

Description

The vulnerability allows a remote attacker to perform a spoofing attack.

The vulnerability exists due to improper certificate validation when processing digital signatures of ODF documents. A remote attacker can modify the documentsignatures.xml or macrosignatures.xml stream within the document to contain both "X509Data" and "KeyValue" children of the "KeyInfo" tag[1], which when opened caused LibreOffice to verify using the "KeyValue" but to report verification with the unrelated "X509Data" value.

Mitigation

Install updates from vendor's website.

Vulnerable software versions

LibreOffice: 7.2.0.1 - 7.3.0.3

External links

http://www.libreoffice.org/about-us/security/advisories/cve-2021-25636/

Q & A

Can this vulnerability be exploited remotely?

Yes. This vulnerability can be exploited by a remote non-authenticated attacker via the Internet.

How the attacker can exploit this vulnerability?

The attacker would have to trick the victim to visit a specially crafted website or open a file.

Is there known malware, which exploits this vulnerability?

No. We are not aware of malware exploiting this vulnerability.