CVE-2026-0773
📋 TL;DR
CVE-2026-0773 is a critical remote code execution vulnerability in Upsonic's Cloudpickle deserialization. Attackers can execute arbitrary code without authentication by sending malicious data to the add_tool endpoint on port 7541. All installations of affected Upsonic versions are vulnerable.
💻 Affected Systems
- Upsonic
⚠️ Manual Verification Required
This CVE does not have specific version information in our database, so automatic vulnerability detection cannot determine if your system is affected.
Why? The CVE database entry doesn't specify which versions are vulnerable (no version ranges provided by the vendor/NVD).
🔒 Custom verification scripts are available for registered users. Sign up free to download automated test scripts.
- Review the CVE details at NVD
- Check vendor security advisories for your specific version
- Test if the vulnerability is exploitable in your environment
- Consider updating to the latest version as a precaution
⚠️ Risk & Real-World Impact
Worst Case
Complete system compromise with attacker gaining full control over the Upsonic server, potentially leading to data theft, lateral movement, and persistent backdoors.
Likely Case
Remote code execution with service account privileges, allowing attackers to install malware, exfiltrate data, or use the system as a foothold for further attacks.
If Mitigated
No impact if proper network segmentation, input validation, and patching are implemented before exploitation attempts.
🎯 Exploit Status
The vulnerability is well-documented with CWE-502 patterns, making exploitation straightforward for attackers familiar with deserialization attacks.
🛠️ Fix & Mitigation
✅ Official Fix
Patch Version: Check vendor advisory for specific version
Vendor Advisory: https://www.zerodayinitiative.com/advisories/ZDI-26-042/
Restart Required: Yes
Instructions:
1. Check the ZDI advisory for patched version information. 2. Update Upsonic to the latest patched version. 3. Restart the Upsonic service to apply changes.
🔧 Temporary Workarounds
Network Access Control
linuxBlock external access to port 7541 using firewall rules
iptables -A INPUT -p tcp --dport 7541 -j DROP
ufw deny 7541/tcp
Endpoint Disablement
allDisable the vulnerable add_tool endpoint if not required
Modify Upsonic configuration to disable or restrict the add_tool endpoint
🧯 If You Can't Patch
- Implement strict network segmentation to isolate Upsonic instances from untrusted networks
- Deploy web application firewall (WAF) rules to block malicious serialized data patterns
🔍 How to Verify
Check if Vulnerable:
Check if Upsonic is running and listening on port 7541: netstat -tlnp | grep 7541 or ss -tlnp | grep 7541Check Version:
Check Upsonic version through its admin interface or configuration filesVerify Fix Applied:
Verify the patched version is installed and test that malicious serialized payloads are rejected📡 Detection & Monitoring
Log Indicators:
- Unusual requests to /add_tool endpoint
- Unexpected process execution from Upsonic service account
- Error logs containing pickle/cPickle deserialization errors
Network Indicators:
- Traffic to port 7541 containing serialized Python objects
- Unusual outbound connections originating from Upsonic server
SIEM Query:
source="upsonic.log" AND ("add_tool" OR "pickle" OR "cPickle")