Vulnerability in nginx (DEBIAN-CVE-2026-9256)

Summary

Vulnerability in nginx (DEBIAN-CVE-2026-9256). Risk of unauthorized operations or information disclosure. Mitigation: upgrade to 1.22.1-9+deb12u8 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 DEBIAN-CVE-2026-9256 has been found in nginx.
Risk of unauthorized operations or information disclosure.
What to do: upgrade nginx to 1.22.1-9+deb12u8 or later.
If unsure, ask your IT team or search "nginx DEBIAN-CVE-2026-9256" on the vendor's site.

DEBIAN-CVE-2026-9256 (nginx)
Patched: 1.22.1-9+deb12u8 — 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 nginx.

📍 Affected scope

Check the vendor advisory for the affected versions of nginx.

🔥 Severity

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

🔧 How to fix

Update to 1.22.1-9+deb12u8.

🛡️ 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 '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

1
Identify 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。
2
Apply patch patch
```
Upgrade nginx to 1.22.1-9+deb12u8
```
ステージング環境で 1.22.1-9+deb12u8 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

Debian:11 nginx

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

Debian:12 nginx

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.22.1-9+deb12u8"}]}]

Debian:13 nginx

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.26.3-3+deb13u6"}]}]

Debian:14 nginx

[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"1.30.1-3"}]}]

References

advisory security-tracker.debian.org