Vulnerability in eglibc (UBUNTU-CVE-2026-4438)

Summary

Vulnerability in eglibc (UBUNTU-CVE-2026-4438). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 2.39-0ubuntu8.8 or later.

Original description

The description as published by the source.

Calling gethostbyaddr or gethostbyaddr_r with a configured nsswitch.conf that specifies the library's DNS backend in the GNU C library version 2.34 to version 2.43 could result in an invalid DNS hostname being returned to the caller in violation of the DNS specification.

Source: OSV.dev (Open Source Vulnerabilities) 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 UBUNTU-CVE-2026-4438 has been found in eglibc.
Risk of unauthorized operations or information disclosure.
What to do: upgrade eglibc to 2.39-0ubuntu8.8 or later.
If unsure, ask your IT team or search "eglibc UBUNTU-CVE-2026-4438" on the vendor's site.

UBUNTU-CVE-2026-4438 (eglibc)
Attack vector: adjacent-network / unauthenticated / no user interaction
Patched: 2.39-0ubuntu8.8 — 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 eglibc.

📍 Affected scope

Check the vendor advisory for the affected versions of eglibc.

🔥 Severity

Severity: ?. Risk of unauthorized operations or information disclosure.

🔧 How to fix

Update to 2.39-0ubuntu8.8.

🛡️ 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 'eglibc' . 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 'eglibc' . | 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 eglibc を grep し、稼働しているサービス・バージョンを把握する。
2
Apply patch patch
```
Upgrade eglibc to 2.39-0ubuntu8.8
```
ステージング環境で 2.39-0ubuntu8.8 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を含めること。
3
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。

Affected packages

Ubuntu:Pro:14.04:LTS eglibc

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

Ubuntu:22.04:LTS glibc

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

Ubuntu:24.04:LTS glibc

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"2.39-0ubuntu8.8"}]}]

Ubuntu:25.10 glibc

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

Ubuntu:26.04:LTS glibc

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

References

advisory ubuntu.com
report ubuntu.com
report cve.org
report sourceware.org
report openwall.com