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CVE-2026-6104 critical CVSS 9.1

Out-of-Bounds Read in libphp (CVE-2026-6104)

Summary

Vulnerability in libphp (CVE-2026-6104). Confidential information can be exposed externally. Mitigation: upgrade to 8.4.21, 8.5.6 or later.

Original description

The description as published by the source.

In PHP versions 8.4.* before 8.4.21 and 8.5.* before 8.5.6, when an encoding name containing an embedded NUL byte is passed to mb_convert_encoding() or related mbstring functions, the code incorrectly assumes that when strncasecmp() returns 0 it means the strings have the same length. This can lead to out-of-bounds read of global memory, potentially causing a crash or information disclosure or crash. Affected functions include mb_convert_encoding(), mb_detect_encoding(), mb_convert_variables(), and mb_detect_order(), as well as the mbstring.detect_order and mbstring.http_output INI settings.

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-2026-6104 has been found in libphp.
Confidential information can be exposed externally. CVSS score: 9.1/10.
What to do: upgrade libphp to 8.4.21, 8.5.6 or later.
If unsure, ask your IT team or search "libphp CVE-2026-6104" on the vendor's site.

CVE-2026-6104 (libphp) — CWE-125 / CVSS v3 9.1
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Patched: 8.4.21, 8.5.6 — 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

Out-of-bounds read (CWE-125) exists in libphp.

📍 Affected scope

Check the vendor advisory for the affected versions of libphp.

🔥 Severity

Severity: Critical (CVSS 9.1/10). Confidential information can be exposed externally.

🔧 How to fix

Update to 8.4.21, 8.5.6.

🛡️ 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 'libphp' . 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. 1
    Identify exposure identify 
    grep -r 'libphp' . | 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 libphp を grep し、稼働しているサービス・バージョンを把握する。

  2. 2
    Apply patch patch 
    Upgrade libphp to 8.4.21, 8.5.6

    ステージング環境で 8.4.21, 8.5.6 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. 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

Bitnami libphp
[{"type":"SEMVER","events":[{"introduced":"8.4.0"},{"fixed":"8.4.21"},{"introduced":"8.5.0"},{"fixed":"8.5.6"}]}]
Bitnami php
[{"type":"SEMVER","events":[{"introduced":"8.4.0"},{"fixed":"8.4.21"},{"introduced":"8.5.0"},{"fixed":"8.5.6"}]}]
Bitnami php-min
[{"type":"SEMVER","events":[{"introduced":"8.4.0"},{"fixed":"8.4.21"},{"introduced":"8.5.0"},{"fixed":"8.5.6"}]}]

Fix status by distribution

Fixed packages published by each distribution for this CVE

References

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