Vulnerability in phpoffice/phpspreadsheet (CVE-2026-59933)
Summary
Vulnerability in phpoffice/phpspreadsheet (CVE-2026-59933). Risk of unauthorized operations or information disclosure. Exploitable via bigBlockChain. Mitigation: upgrade to 1.30.6 or later.
Original description
The description as published by the source.
PhpSpreadsheet is a pure PHP library for reading and writing spreadsheet files. In versions 4.0.0 through 5.8.0, 3.3.0 through 3.10.6, 2.2.0 through 2.4.6, 2.0.0 through 2.1.17, and all releases up to and including 1.30.5, the OLE reader follows sector chains from attacker-controlled XLS/OLE metadata without detecting cycles or enforcing a maximum chain length. A tiny malformed .xls/OLE file can set the small-block depot sector chain to point back to itself. During normal XLS detection, OLERead::read() appends the same sector data repeatedly until the PHP process exhausts memory. This is reachable from Reader\Xls::canRead() and therefore from automatic spreadsheet type detection. Applications that accept attacker-controlled spreadsheet uploads can suffer denial of service from a very small file. This issue has been fixed in versions 5.8.1, 3.10.7, 2.4.7, 2.1.18 and 1.30.6.
Source: GitHub Security Advisories (Global) 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-2026-59933 has been found in phpoffice/phpspreadsheet.
Attackers can target a specific entry point like bigBlockChain over the network to misuse the product.
Risk of unauthorized operations or information disclosure. CVSS score: 7.5/10.
What to do: upgrade phpoffice/phpspreadsheet to 1.30.6 or later.
If unsure, ask your IT team or search "phpoffice/phpspreadsheet CVE-2026-59933" on the vendor's site.
CVE-2026-59933 (phpoffice/phpspreadsheet) — CWE-400 / CVSS v3 7.5
Attack vector: remote (network-reachable) / unauthenticated / no user interaction
Attack surface: bigBlockChain
Patched: 1.30.6 — 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.
A vulnerability (CWE-400) exists in phpoffice/phpspreadsheet. Attackers reach the vulnerable code path via bigBlockChain without authentication.
Check the vendor advisory for the affected versions of phpoffice/phpspreadsheet. Attack surface: bigBlockChain.
Severity: High (CVSS 7.5/10). Risk of unauthorized operations or information disclosure.
Update to 1.30.6.
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 'phpoffice/phpspreadsheet' . 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 'phpoffice/phpspreadsheet' . | 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
phpoffice/phpspreadsheet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 phpoffice/phpspreadsheet to 1.30.6ステージング環境で 1.30.6 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。
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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 github.com
- advisory github.com
- advisory nvd.nist.gov
- package github.com
- patch github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com
- web github.com