Vulnerability in nginx (UBUNTU-CVE-2026-9256)
Summary
Vulnerability in nginx (UBUNTU-CVE-2026-9256). Successful exploitation can lead to full system takeover. Mitigation: upgrade to 1.4.6-1ubuntu3.9+esm6 or later.
Original description
The description as published by the source.
NGINX Plus and NGINX Open Source have a vulnerability in the ngx_http_rewrite_module module. This vulnerability exists when a rewrite directive uses a regex pattern with distinct, overlapping Perl-Compatible Regular Expression (PCRE) captures (for example, ^/((.*))$) and a replacement string that references multiple such captures (for example, $1$2) in a redirect or arguments context. An unauthenticated attacker along with conditions beyond their control can exploit this vulnerability by sending crafted HTTP requests. This may cause a heap buffer overflow in the NGINX worker process leading to a restart. Additionally, attackers can execute code on systems with Address Space Layout Randomization (ASLR) disabled or when the attacker can bypass ASLR. Note: Software versions which have reached End of Technical Support (EoTS) are not evaluated.
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-2026-9256 has been found in nginx.
Successful exploitation can lead to full system takeover.
What to do: upgrade nginx to 1.4.6-1ubuntu3.9+esm6 or later.
If unsure, ask your IT team or search "nginx UBUNTU-CVE-2026-9256" on the vendor's site.
UBUNTU-CVE-2026-9256 (nginx)
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 1.4.6-1ubuntu3.9+esm6 — 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.
A vulnerability (unclassified) exists in nginx.
Check the vendor advisory for the affected versions of nginx.
Severity: ?. Successful exploitation can lead to full system takeover.
Update to 1.4.6-1ubuntu3.9+esm6.
Until the patch is applied: disable the affected feature, apply WAF rules, or restrict access via network ACLs.
Search webserver/proxy logs for unusual request patterns matching this CVE's known IOCs. Run grep -r 'nginx' . 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
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1Identify exposure identify
grep -r 'nginx' . | 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
nginxを grep し、稼働しているサービス・バージョンを把握する。 -
2Apply patch patch
Upgrade nginx to 1.4.6-1ubuntu3.9+esm6ステージング環境で 1.4.6-1ubuntu3.9+esm6 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。
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3Post-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
References
- advisory ubuntu.com
- advisory ubuntu.com
- report ubuntu.com
- report cve.org
- report my.f5.com
- report openwall.com