CVE-2025-40843

CodeChecker versions up to 6.26.1 contain a buffer overflow vulnerability in the internal ldlogger library, which is executed by the CodeChecker log command.

Details

Unsafe usage of strcpy() function in the internal ldlogger library allows attackers to trigger a buffer overflow by supplying crafted inputs from the command line. Specifically, the destination buffer is stack-allocated with a fixed size of 4096 bytes, while strcpy() is called without any length checks, enabling an attacker to overrun the buffer.

PoC

Example script is included below to illustrate how this vulnerability can be exploited.

#!/bin/bash

export CC_LOGGER_DEF_DIRS=1; 
payload=''; for i in $(seq 1 4090); do payload+='A'; done

CodeChecker log -b "/very/long/path/to/$payload/gcc a.c" -o compilation.json

Any environment where the vulnerable CodeChecker log command is executed with untrusted user input is affected by this vulnerability.

CVE-2025-40843 has a CVSS score of 5.9 (Medium). The vector is requires local access, no privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (6.26.2); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2025-40843? CVE-2025-40843 is a medium-severity security vulnerability in codechecker (pip), affecting versions <= 6.26.1. It is fixed in 6.26.2.
2. How severe is CVE-2025-40843? CVE-2025-40843 has a CVSS score of 5.9 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of codechecker are affected by CVE-2025-40843? codechecker (pip) versions <= 6.26.1 is affected.
4. Is there a fix for CVE-2025-40843? Yes. CVE-2025-40843 is fixed in 6.26.2. Upgrade to this version or later.
5. Is CVE-2025-40843 exploitable, and should I be worried? Whether CVE-2025-40843 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2025-40843 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2025-40843? Upgrade codechecker to 6.26.2 or later.