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CVE-2025-23016

30
FAUCET Score

CVE-2025-23016 is a critical integer overflow vulnerability in FastCGI fcgi2 versions 2.x through 2.4.4, specifically in the ReadParams function of fcgiapp.c, which can lead to a heap-based buffer overflow via crafted nameLen or valueLen data sent to the IPC socket. With a CVSS score of 9.3 (CRITICAL), this vulnerability is remotely exploitable with low attack complexity, requiring no user interaction, and can result in complete compromise of confidentiality, integrity, and availability. While there is no evidence of active exploitation, a public exploit write-up exists, and the vulnerability has garnered some community discussion, indicating potential for future exploitation.

Impacted Technologies

VendorProductVersion(s)CPE
>= 2.0.0, <= 2.4.4CPE match
cpe:2.3:a:fastcgi:fcgi:*:*:*:*:*:*:*:*

CVSS Data

CVSS version used by this source: 3.1

9.3CRITICAL

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

Attack Vector
LOCAL
Attack Complexity
LOW
Privileges Required
NONE
User Interaction
NONE
Scope
CHANGED
Confidentiality Impact
HIGH
Integrity Impact
HIGH
Availability Impact
HIGH
Exploitability Score
2.5
Impact Score
6.0
CvssVersion
3.1

Exploit Intelligence

EPSS Score
0.57%
Probability of exploitation in next 30 days
EPSS Percentile
43.6%
Percentile rank of EPSS score among Peer Group
As of 2026-07-27
Model: v2026.06.15
This CVE's current EPSS score of 0.0057 is in the 91st percentile among its peer group of 79 CVEs.

Social Chatter

The average CVE in this peer group has 0.0 Twitter, 0.1 Reddit, 0.7 Bluesky, 0.3 Mastodon, and 1.0 GitHub mentions.

Media Mentions

No media coverage found for this CVE.

The average CVE in this peer group has 0.3 InfoSec Media, 0.0 Vendor Blog, and 0.0 Security Researcher mentions.

Remediation

Patch Available

Vendor Patches (9)

microsoftpatch availablevia msrc
Product: 19226-17084Fixed in: 2.4.5-1
microsoftpatch availablevia msrc
Product: 19351-16823Fixed in: 2.4.5-1
microsoftpatch availablevia msrc
Product: 19352-17084Fixed in: 2.4.5-1
microsoftpatch availablevia msrc
Product: 19225-17086Fixed in: 2.4.5-1
microsoftpatch availablevia msrc
Product: 20222-17086Fixed in: 2.4.5-1
microsoftpatch availablevia msrc
Product: cbl2 fcgi 2.4.0-7 on CBL Mariner 2.0Fixed in: 2.4.5-1
microsoftpatch availablevia msrc
Product: azl3 fcgi 2.4.0-7 on Azure Linux 3.0Fixed in: 2.4.5-1
microsoftpatch availablevia msrc
Product: cbl2 fcgi 2.4.5-1 on CBL Mariner 2.0Fixed in: 2.4.5-1
microsoftpatch availablevia msrc
Product: azl3 fcgi 2.4.5-1 on Azure Linux 3.0Fixed in: 2.4.5-1

Vendor Advisories (1)

microsoft2025-Jan/CVE-2025-23016

FastCGI fcgi2 (aka fcgi) 2.x through 2.4.4 has an integer overflow (and resultant heap-based buffer overflow) via crafted nameLen or valueLen values in data to the IPC socket. This occurs in ReadParams in fcgiapp.c.

Jan 14, 2025

References

lists.debian.org / debian-lts-announce/2025/10/msg00009.html
openwall.com / lists/oss-security/2025/04/23/4
github.com / FastCGI-Archives/fcgi2/issues/67
github.com / FastCGI-Archives/fcgi2/releases/tag/2.4.5
synacktiv.com / en/publications/cve-2025-23016-exploiting-the-fastcgi-library