CVE-2021-21703

HIGHNVD 7.87.8—
EchelonGraph scoreMEDIUM confidence

This high-severity CVE scores 7.8 under NVD CVSS v3. EPSS exploit probability: 1.3%, top 32% of all CVEs by exploit prediction. GitHub Security Advisory enrichment pending alignment with NVD CVSS.

Triggered by: NVD CVSS baseline
Sources: epss, ghsa, nvd
Trending — 3 sources updated this week
7.8
EchelonGraph verdictPlan a fixSerious severity, but no confirmed exploitation yet.
  • High severity, but no confirmed exploitation yet
CISA-KEV: Not listedEPSS: 1%CVSS: 7.8Exploit: NoneExposed: 0

A fix is available — apply it.

In PHP versions 7.3.x up to and including 7.3.31, 7.4.x below 7.4.25 and 8.0.x below 8.0.12, when running PHP FPM SAPI with main FPM daemon process running as root and child worker processes running as lower-privileged users, it is possible for the child processes to access memory shared with the main process and write to it, modifying it in a way that would cause the root process to conduct invalid memory reads and writes, which can be used to escalate privileges from local unprivileged user to the root user.

CVSS v3
7.8
EG Score
7.8(medium)
EG Risk
—
EPSS
68.3%
KEV
Not listed

Published

October 25, 2021

Last Modified

November 21, 2024

References (24)

Vendor Advisories for CVE-2021-21703(1)

These vendors published their own advisory mentioning this CVE — often with vendor-specific remediation steps + affected product lists not in NVD.

Patch Availability(3)

Vendor / EcosystemFixed in / PatchReleasedSource
ubuntuphp7.0-zip (7.0.33-0ubuntu0.16.04.16+esm2) @ xenial2026-05-26ubuntu
redhatrh-php73-php-0:7.3.33-1.el72022-07-04redhat
redhatphp:7.4-8060020220120080432.0a326c832022-05-10redhat

Patches are aggregated from vendor advisories (Red Hat, Microsoft, Cisco, GitHub) and package ecosystems (OSV, GHSA). Multiple rows for the same upstream release have been deduplicated.

Weakness Classification(2)

MITRE Common Weakness Enumeration — the root-cause categories this CVE belongs to.

Additional Vendor Advisories

(3)

Vendors that published advisories for this CVE beyond the curated set above. Broader coverage but minimal per-row detail — click through for the original advisory.

Data Freshness Timeline

(refreshed 10× in last 7d / 46× in last 30d)

Each row is a source pipeline that fetched or updated this CVE on that date, with what changed. For example, "NVD update" means NVD published or revised its analysis for this CVE; "MITRE cvelistV5" means we ingested or refreshed it from the CNA feed. Most recent first.

Showing the most recent 100 of 101 total refreshes for this CVE.

  1. 2026-07-22 22:43 UTCEG score recompute▲ 0.80
  2. 2026-07-22 14:05 UTCEPSS rescore
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  39. 2026-06-12 18:10 UTCOSV refresh
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  71. 2026-05-26 08:32 UTCEG score recompute
  72. 2026-05-26 08:32 UTCVendor advisory
  73. 2026-05-26 08:32 UTCGHSA enrichment
  74. 2026-05-26 07:17 UTCEPSS rescore
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Frequently asked(5)

What is CVE-2021-21703?
CVE-2021-21703 is a high vulnerability published on October 25, 2021. In PHP versions 7.3.x up to and including 7.3.31, 7.4.x below 7.4.25 and 8.0.x below 8.0.12, when running PHP FPM SAPI with main FPM daemon process running as root and child worker processes running as lower-privileged users, it is possible for the child processes to access memory shared with the…
When was CVE-2021-21703 disclosed?
CVE-2021-21703 was first published in the National Vulnerability Database on October 25, 2021, with the most recent update on November 21, 2024. EchelonGraph re-ingests CVE updates from NVD on a 2-hour cycle, so this page reflects the latest published state.
Is CVE-2021-21703 actively exploited?
CVE-2021-21703 is not currently on CISA's Known Exploited Vulnerabilities catalog. FIRST EPSS estimates a 68.3% percentile likelihood of exploitation in the next 30 days — higher percentiles indicate greater predicted risk.
What is the CVSS score of CVE-2021-21703?
CVE-2021-21703 has a CVSS v3 base score of 7.8 (NVD).
How do I remediate CVE-2021-21703?
Patch to the fixed version published by the affected vendor. Where vendor advisories exist for CVE-2021-21703, EchelonGraph cross-links them in the Vendor Advisories panel below — those typically contain the canonical remediation steps, fixed version numbers, and any vendor-specific mitigations.

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