How severe is CVE-2021-21706?

CVE-2021-21706 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability none.

Is CVE-2021-21706 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (71st percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-21706?

CVE-2021-21706 affects Php. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2021-21706?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-21706 published?

CVE-2021-21706 was published on 2021-10-04 and last updated on 2026-06-17.

CVE-2021-21706

CVE-2021-21706 is a medium-severity vulnerability in Php with a CVSS 3.x base score of 5.3. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-22.

Key facts

Severity: Medium (CVSS 3.x base score 5.3)
CVSS v2: 4.3
EPSS exploit prediction: 1% (71st percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-22
Affected product: Php
Published: 2021-10-04
Last modified: 2026-06-17

Description

In PHP versions 7.3.x below 7.3.31, 7.4.x below 7.4.24 and 8.0.x below 8.0.11, in Microsoft Windows environment, ZipArchive::extractTo may be tricked into writing a file outside target directory when extracting a ZIP file, thus potentially causing files to be created or overwritten, subject to OS permissions.

Frequently asked questions

What is CVE-2021-21706?: In PHP versions 7.3.x below 7.3.31, 7.4.x below 7.4.24 and 8.0.x below 8.0.11, in Microsoft Windows environment, ZipArchive::extractTo may be tricked into writing a file outside target directory when extracting a ZIP file, thus potentially causing files to be created or overwritten, subject to OS permissions.
How severe is CVE-2021-21706?: CVE-2021-21706 has a CVSS 3.x base score of 5.3, rated medium severity. It is exploitable over network with high attack complexity, requires no privileges and user interaction. Impact on confidentiality is none, integrity high, and availability none.
Is CVE-2021-21706 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (71st percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-21706?: CVE-2021-21706 affects Php. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2021-21706?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-21706 published?: CVE-2021-21706 was published on 2021-10-04 and last updated on 2026-06-17.

References

Affected products (1)

cpe:2.3:a:php:php:*:*:*:*:*:*:*:*

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Threat intelligence

Threat-intel indicators referencing this CVE:

20.157.117.15 (ipv4-addr)
223.197.186.7 (ipv4-addr)
218.51.148.194 (ipv4-addr)
103.174.34.49 (ipv4-addr)
34.83.189.112 (ipv4-addr)
220.178.39.106 (ipv4-addr)
158.94.210.133 (ipv4-addr)
61.7.144.60 (ipv4-addr)