Vulnerability in LibreOffice (CVE-2021-25635)

Summary

Vulnerability in LibreOffice (CVE-2021-25635). Data can be tampered with by attackers.

Original description

The description as published by the source.

An Improper Certificate Validation vulnerability in LibreOffice allowed
an attacker to self sign an ODF document, with a signature untrusted by
the target, then modify it to change the signature algorithm to an
invalid (or unknown to LibreOffice) algorithm and LibreOffice would incorrectly present such a signature with an unknown algorithm as a
valid signature issued by a trusted person

This issue affects LibreOffice: from 7.0 before 7.0.5, from 7.1 before 7.1.1.

Source: OSV.dev (Open Source Vulnerabilities) NVD OSV

Auto-generated summary

Assembled by SecPulse from the source data (CVSS, CWE, affected versions) using templates — no AI involved. Check the original description and references below for exact details.

A vulnerability tracked as CVE-2021-25635 has been found in LibreOffice.
Data can be tampered with by attackers.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "LibreOffice CVE-2021-25635" on the vendor's site.

CVE-2021-25635 (LibreOffice)
Attack vector: local / no user interaction
Plan: 1) Audit SBOM/dependencies, 2) Stage→prod upgrade, 3) Add WAF/proxy monitoring on affected endpoints, 4) Hunt IOCs in logs.
Refs: see the GHSA / vendor advisory / patched release linked on this page.

❓ What is the problem

A vulnerability (unclassified) exists in LibreOffice.

📍 Affected scope

Check the vendor advisory for the affected versions of LibreOffice.

🔥 Severity

Severity: ?. Data can be tampered with by attackers.

🔧 How to fix

Update to the patched release per vendor advisory.

🛡️ Workaround

Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.

🔍 Detection

Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'LibreOffice' . against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response actions

Concrete steps and command examples for SOC/SRE teams to execute in order

1
Identify exposure identify
```
grep -r 'LibreOffice' . | grep -v node_modules
```
リポジトリと本番環境の依存ファイル (package-lock.json / requirements.txt / go.sum / Gemfile.lock 等) で LibreOffice を grep し、稼働しているサービス・バージョンを把握する。
2
Post-deployment verification verify
```
Confirm patched version is live in production
```
パッチ適用後、ステージングで PoC または同等の悪用パターンを再現して脆弱性が閉じたことを確認。本番ではアクセスログ・WAF でアラート再発が無いか継続監視。

References

advisory libreoffice.org