CVE-2021-21704
CWE-125Published: October 4, 2021· Updated: Jun 17, 2026
Official Description
In PHP versions 7.3.x below 7.3.29, 7.4.x below 7.4.21 and 8.0.x below 8.0.8, when using Firebird PDO driver extension, a malicious database server could cause crashes in various database functions, such as getAttribute(), execute(), fetch() and others by returning invalid response data that is not parsed correctly by the driver. This can result in crashes, denial of service or potentially memory corruption.
Technical Analysis
CVE-2021-21704 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.
The vulnerability requires no privileges and no user interaction, making it a prime target for automated exploitation campaigns and worm-like propagation.
A successful exploit results in availability disruption (denial of service), with a CVSS base score of 5.9.
CVSS v3.1 Vector Breakdown
Affected Vendors & Products
Exploit & PoC Resources
Official Patches & Advisories
All References (12)
Quick Facts
Related CVEs (CWE-125)
Recommended Actions
- →Apply vendor patches immediately
- →Monitor CVE-2021-21704 in threat intel feeds
- →Review IDS/IPS signatures for exploitation attempts