Path Traversal in contao/core-bundle (CVE-2026-107844)
Summary
Path traversal in contao/core-bundle (CVE-2026-107844). Risk of unauthorized operations or information disclosure. Exploitable via ImagesController. Mitigation: upgrade to 5.7.12 or later.
Original description
The description as published by the source.
ImagesController joins the user controlled {path} onto the configured image target directory with Path::join(), which canonicalises .. segments, and never calls Path::isBasePath() to confirm the result stayed inside that directory. An unauthenticated GET with percent encoded dot segments therefore escapes the directory and the file is returned by BinaryFileResponse. Reads are bounded to the extensions in contao.image.valid_extensions, and paths below the upload directory fail for an unrelated reason, so this is reported as a missing boundary check rather than as a general arbitrary file read. Both Apache with the shipped public/.htaccess and nginx with the documented configuration are affected.
Impact
Any unauthenticated visitor can read files that are deliberately kept outside the document root, anywhere under the project directory, as long as the name ends in one of contao.image.valid_extensions (jpg, jpeg, gif, png, tif, tiff, bmp, svg, svgz, webp). The route also acts as an existence oracle for arbitrary paths, and on a debug enabled instance the 404 message discloses the absolute filesystem path.
Honesty caveat, stated because it lowers the severity. The reporter could not use this to read protected member folders: every path below the upload directory returns 500 for the reason given under Details, so the practically reachable set is image typed files outside files/.
Source: NIST National Vulnerability Database NVD GitHub Advisory
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-2026-107844 has been found in contao/core-bundle.
Attackers can target a specific entry point like ImagesController over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 5.3/10.
What to do: upgrade contao/core-bundle to 5.7.12 or later.
If unsure, ask your IT team or search "contao/core-bundle CVE-2026-107844" on the vendor's site.
CVE-2026-107844 (contao/core-bundle) — CWE-22 / CVSS v3 5.3
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: ImagesController / BinaryFileResponse / contao.image.valid_extensions / jpg
Patched: 5.7.12 — 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.
Path traversal (CWE-22) exists in contao/core-bundle. Attackers reach the vulnerable code path via ImagesController without authentication.
Check the vendor advisory for the affected versions of contao/core-bundle. Attack surface: ImagesController / BinaryFileResponse / contao.image.valid_extensions / jpg.
Severity: Medium (CVSS 5.3/10). Risk of unauthorized operations or information disclosure.
Update to 5.7.12.
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 'contao/core-bundle' . 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 'contao/core-bundle' . | 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
contao/core-bundle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 contao/core-bundle to 5.7.12ステージング環境で 5.7.12 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。