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UBUNTU-CVE-2018-20843

Vulnerability in expat (UBUNTU-CVE-2018-20843)

Summary

vulnerability in expat (UBUNTU-CVE-2018-20843). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to `2.1.0-4ubuntu1.4+esm1` or later.

AI summary snake-internal / snake-material-v2

A vulnerability tracked as **UBUNTU-CVE-2018-20843** has been found in expat. Risk of unauthorized operations or information disclosure. CVSS score: ?/10. What to do: upgrade expat to **2.1.0-4ubuntu1.4+esm1** or later. If unsure, ask your IT team or search "expat UBUNTU-CVE-2018-20843" on the vendor's site.

UBUNTU-CVE-2018-20843 (expat) — Attack vector: remote (network-reachable) / unauthenticated / no user interaction Patched: `2.1.0-4ubuntu1.4+esm1` — apply immediately 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 expat.

📍 Affected scope

expat — .

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure

🔧 How to fix

Update to **2.1.0-4ubuntu1.4+esm1**.

🛡️ 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 'expat' .` against your dependency files (package-lock.json, requirements.txt, go.sum) to find affected services.

Response Actions (7 steps)

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

1
Identify exposure identify
```
grep -r 'expat' . | 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 `expat` を grep し、稼働しているサービス・バージョンを把握する。
6
Apply patch patch
```
Upgrade expat to 2.1.0-4ubuntu1.4+esm1
```
ステージング環境で 2.1.0-4ubuntu1.4+esm1 に上げて回帰テスト → 本番反映。回帰テストはアプリの主要ハッピーパスと、Step 3 で見つけた異常検知の続報チェックを含めること。
7
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 Step 3 と同じログクエリでアラート再発が無いか継続監視。

Affected packages

Ubuntu:Pro:14.04:LTS expat

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.1.0-4ubuntu1.4+esm1"}]}]

Ubuntu:Pro:14.04:LTS vtk

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.8.0-14.1ubuntu3+esm1"}]}]

Ubuntu:Pro:14.04:LTS coin3

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:14.04:LTS vnc4

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:14.04:LTS xmlrpc-c

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:16.04:LTS expat

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.1.0-7ubuntu0.16.04.4"}]}]

Ubuntu:Pro:16.04:LTS libxmltok

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.2-3ubuntu0.16.04.1~esm2"}]}]

Ubuntu:Pro:16.04:LTS vtk

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"5.10.1+dfsg-2.1ubuntu0.1~esm1"}]}]

Ubuntu:16.04:LTS ayttm

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:16.04:LTS cableswig

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:16.04:LTS cadaver

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:16.04:LTS coin3

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:16.04:LTS insighttoolkit

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:16.04:LTS insighttoolkit4

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:16.04:LTS matanza

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:16.04:LTS swish-e

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:16.04:LTS vnc4

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:16.04:LTS xmlrpc-c

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:18.04:LTS expat

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.2.5-3ubuntu0.1"}]}]

Ubuntu:18.04:LTS cadaver

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:18.04:LTS coin3

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:18.04:LTS libxmltok

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.2-4ubuntu0.18.04.1~esm4"}]}]

Ubuntu:18.04:LTS matanza

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:18.04:LTS swish-e

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:18.04:LTS vnc4

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:18.04:LTS xmlrpc-c

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:20.04:LTS cadaver

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:20.04:LTS libxmltok

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.2-4ubuntu0.20.04.1~esm4"}]}]

Ubuntu:20.04:LTS matanza

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:20.04:LTS swish-e

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:20.04:LTS xmlrpc-c

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:22.04:LTS cadaver

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:22.04:LTS matanza

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:22.04:LTS xmlrpc-c

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:22.04:LTS libxmltok

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.2-4ubuntu0.22.04.1~esm4"}]}]

Ubuntu:Pro:22.04:LTS swish-e

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:24.04:LTS cadaver

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:24.04:LTS matanza

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:24.04:LTS xmlrpc-c

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:24.04:LTS libxmltok

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.2-4.1ubuntu2.24.0.4.1+esm2"}]}]

Ubuntu:Pro:24.04:LTS swish-e

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:25.10 cadaver

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:25.10 matanza

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:25.10 sitecopy

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:25.10 swish-e

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:25.10 xmlrpc-c

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:26.04:LTS cadaver

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:26.04:LTS matanza

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:26.04:LTS sitecopy

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:26.04:LTS xmlrpc-c

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:26.04:LTS swish-e

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:14.04:LTS xmlrpc-c

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:16.04:LTS ayttm

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:16.04:LTS xmlrpc-c

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:18.04:LTS xmlrpc-c

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:20.04:LTS xmlrpc-c

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:22.04:LTS xmlrpc-c

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:24.04:LTS xmlrpc-c

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

Ubuntu:Pro:16.04:LTS cableswig

[{"type":"ECOSYSTEM","events":[{"introduced":"0"}]}]

References

advisory https://ubuntu.com/security/notices/USN-4040-1
advisory https://ubuntu.com/security/notices/USN-4040-2
advisory https://ubuntu.com/security/notices/USN-5455-1
advisory https://ubuntu.com/security/notices/USN-4852-1
advisory https://ubuntu.com/security/notices/USN-7199-1
report https://ubuntu.com/security/CVE-2018-20843
report https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=5226
report https://github.com/libexpat/libexpat/pull/262
report https://github.com/libexpat/libexpat/blob/R_2_2_7/expat/Changes
report https://github.com/libexpat/libexpat/pull/262/commits/11f8838bf99ea0a6f0b76f9760c43704d00c4ff6
report https://www.cve.org/CVERecord?id=CVE-2018-20843

Summary

AI summary snake-internal / snake-material-v2

Response Actions (7 steps)

Affected packages

References

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