Out-of-Bounds Write in Oracle Xmlsoft (CVE-2021-3517, CVSS 8.6)

Summary

Out-of-bounds write in Oracle Xmlsoft (CVE-2021-3517). Risk of unauthorized operations or information disclosure.

Original description

The description as published by the source.

There is a flaw in the xml entity encoding functionality of libxml2 in versions before 2.9.11. An attacker who is able to supply a crafted file to be processed by an application linked with the affected functionality of libxml2 could trigger an out-of-bounds read. The most likely impact of this flaw is to application availability, with some potential impact to confidentiality and integrity if an attacker is able to use memory information to further exploit the application.

Source: NIST National Vulnerability Database NVD

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-2021-3517 has been found in Oracle Xmlsoft.
Risk of unauthorized operations or information disclosure. CVSS score: 8.6/10.
What to do: apply the vendor's official patched release.
If unsure, ask your IT team or search "Oracle Xmlsoft CVE-2021-3517" on the vendor's site.

CVE-2021-3517 (Oracle Xmlsoft) — CWE-787 / CVSS v3 8.6
Attack vector: remote (network-reachable) / unauthenticated / 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

Out-of-bounds write (CWE-787) exists in Oracle Xmlsoft.

📍 Affected scope

Check the vendor advisory for the affected versions of Oracle Xmlsoft.

🔥 Severity

Severity: High (CVSS 8.6/10). Risk of unauthorized operations or information disclosure.

🔧 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 'Xmlsoft' . 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 'Xmlsoft' . | 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 Xmlsoft 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。

Fix status by distribution

Fixed packages published by each distribution for this CVE

Alpine Linux ALPINE-CVE-2021-3517 libxml2 Fixed in: 2.9.9-r5

Out-of-Bounds Write in Oracle Xmlsoft (CVE-2021-3517)

Summary

Original description

Auto-generated summary

Response actions

Fix status by distribution

References