CVE-2025-40843 is a medium-severity (CVSS 5.9) CWE-121 vulnerability in codechecker. A fix is available for codechecker — see the affected versions and patch details below.
Buffer overflow in CodeChecker log command
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-40843.
EPSS Exploitation Probability
Probability of exploitation in the next 30 days, from FIRST.org EPSS.
How urgent is this, really
Where this sits among everything scored
Real-World Exposure
codecheckerReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects PyPI packages — download data is not available via public APIs for these ecosystems.
Description
Summary
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
Impact
Any environment where the vulnerable CodeChecker log command is executed with untrusted user input is affected by this vulnerability.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐍PyPI | codechecker | all versions | 6.26.2pip install --upgrade 'codechecker==6.26.2' |
Affected Products
codecheckerericssonDetection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for codechecker, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update codechecker to 6.26.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-40843 is resolved across your whole dependency graph.
Workarounds
Stop feeding it untrusted input: reject or quarantine files and payloads from unverified sources until you can upgrade, restrict accepted formats to the ones you actually need, and run the parsing or decoding step in a least-privileged sandbox or short-lived worker so a crash or corrupted read cannot reach the rest of the process.
Frequently Asked Questions
Is CVE-2025-40843 in your dependencies?
Find it across PyPI, including transitive dependencies.