CVE-2026-59933: 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, an

highCVSS 7.5CVE-2026-59933

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.

Details

Source: NVD Recent CVEs (US · database · site)
Severity: high — CVSS 7.5
Published: 2026-07-28
Last updated: 2026-07-30
Exploitation: Not in CISA KEV at last sync

Original advisory: https://nvd.nist.gov/vuln/detail/CVE-2026-59933

Exploitation outlook

EPSS (FIRST.org) estimates each CVE’s probability of exploitation in the next 30 days — here is the CSIRTS.com read on those numbers.

Low exploitation riskCVE-2026-599330.69% 30-day exploitation probability — currently an unlikely target, but scores change as exploit code circulates. Riskier than 49% of all scored CVEs.

Referenced CVEs

CVE	CSIRTS overview	External
CVE-2026-59933	coverage & exploitation status	NVD · CVE.org

Same CVEs, other sources

How other CERTs, PSIRTs and databases cover the vulnerabilities in this advisory.

highGHSA-xh5m-36r6-47m3: PHPSpreadsheet: XLS/OLE sector-chain self-loop causes memory exhaustionghsa

Recent advisories for PhpSpreadsheet is a

A cluster of recent advisories against the same product widens the attack surface — attackers routinely chain freshly published CVEs on one product, so review these together.

highCVE-2026-59932: PhpSpreadsheet is a pure PHP library for reading and writing spreadsheet files. In versions 4.…nvd · 2026-07-28
highCVE-2026-59931: PhpSpreadsheet is a pure PHP library for reading and writing spreadsheet files. In versions 4.…nvd · 2026-07-28
highGHSA-xh5m-36r6-47m3: PHPSpreadsheet: XLS/OLE sector-chain self-loop causes memory exhaustionghsa · 2026-07-23
highGHSA-2mrg-gjxq-2gvr: PHPSpreadsheet: Gnumeric reader unbounded gzip expansion causes memory exhaustionghsa · 2026-07-23
highGHSA-6hq5-7373-42rg: PHPSpreadsheet: SSRF bypass via HTTP redirect in WEBSERVICE() domain whitelistghsa · 2026-07-23