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CVE-2021-21703

HIGHCVSS 7/10EPSS 1.34%

Last modified

CVE-2021-21703 is a high-severity vulnerability rated 7/10 on the CVSS scale. 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.. EPSS estimates a 1.34% chance of exploitation in the next 30 days.

Description

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.

Metrics

CVSS 3.1
7/10

CVSS:3.1/AV:L/AC:H/PR:L/UI:N/S:U/C:H/I:H/A:H

EPSS Probability
1.34%

67.7th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
PhpPhp>= 7.3.0, <= 7.3.31
PhpPhp>= 7.4.0, < 7.4.25
PhpPhp>= 8.0.0, < 8.0.12
DebianDebian Linux9.0
DebianDebian Linux10.0
DebianDebian Linux11.0
FedoraprojectFedora33
FedoraprojectFedora34
FedoraprojectFedora35
NetappClustered Data OntapAll versions
OracleCommunications Diameter Signaling Router>= 8.0.0.0, <= 8.5.0.2

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2021-21703?
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.
How severe is CVE-2021-21703?
CVE-2021-21703 has a CVSS score of 7/10 (HIGH severity). The EPSS model estimates a 1.34% probability of exploitation in the next 30 days.
How do I fix CVE-2021-21703?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

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Source: NVD / NIST