CVE-2025-40907
Description
A flaw was found in the FCGI library. In affected versions, specially crafted nameLen or valueLen values in data sent to the IPC socket may result in a heap-based buffer overflow, which can cause an application crash or other undefined behavior. This occurs in ReadParams in fcgiapp.c.
Statement
This vulnerability is Important rather than just a Moderate flaw because it stems from an integer overflow in the allocation size calculation during parameter parsing in the FastCGI implementation. When the application processes incoming FastCGI parameters, it calculates the total size of memory to allocate by adding the name and value lengths along with two additional bytes. On 32-bit systems, this arithmetic operation can wrap around (due to the limited 32-bit size of size_t), leading to a significantly smaller allocation than intended. However, subsequent calls to FCGX_GetStr use the original (large) lengths provided by the attacker and write far beyond the allocated memory region (heap overflow). Unlike a moderate vulnerability (e.g., memory leak or a simple read out-of-bounds), this heap overflow directly allows an attacker to overwrite adjacent memory in the heap in a controlled way, potentially leading to arbitrary code execution, data corruption, or privilege escalation.
Mitigation
No mitigation is currently available that meets Red Hat Product Security’s standards for usability, deployment, applicability, or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 7.5 | N/A | 5.3 |
| Attack Vector | Network | N/A | Network |
| Attack Complexity | Low | N/A | Low |
| Privileges Required | None | N/A | None |
| User Interaction | None | N/A | None |
| Scope | Unchanged | N/A | Unchanged |
| Confidentiality | None | N/A | None |
| Integrity Impact | None | N/A | None |
| Availability Impact | High | N/A | Low |
Vector
Red Hat: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
cve.org: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
Understanding the Weakness (CWE)
Confidentiality,Integrity,Availability
Technical Impact: Varies by Context
The consequences vary widely, depending on the vulnerabilities that exist in the component; how those vulnerabilities can be "reached" by adversaries, as the exploitation paths and attack surface will vary depending on how the component is used; and the criticality of the privilege levels and features for which the product relies on the component.
Frequently Asked Questions
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