⚠ Reference material — not professional advice. Test in staging, back up first, verify against your specific version. Use your own judgment for your environment.
● Medium · CVSS 5.3

How to Fix CVE-2026-1813: Unrestricted File Upload in bolo-solo

Other vulnerabilities in the same area that are worth patching alongside this one:

*By Sai Kiran Pandrala*

⚡ At a glance
SeverityCVSS 5.3 - Medium
Actively exploited?Not currently listed in CISA KEV
Affected2.6.0, 2.6.1, 2.6.2, 2.6.3, 2.6.4
Fixed inSee vendor advisory
Type (CWE)CWE-434: Unrestricted Upload

What is CVE-2026-1813?

CVE-2026-1813 is an unrestricted file upload flaw in bolo-solo. An attacker can upload files of arbitrary type or to arbitrary locations, leading to webshell deployment and remote code execution. Vendor description: A vulnerability was found in bolo-blog bolo-solo up to 2.6.4. Affected is an unknown function of the file src/main/java/org/b3log/solo/bolo/pic/PicUploadProcessor.java of the component FreeMarker Template Handler.

Why this CVE matters

Unrestricted file upload is the classic webshell vector. The attacker uploads a script with an executable extension, then requests it through the same web server to execute commands.

For deployments of bolo-solo that have been exposed to the public internet during the disclosure window, the operating assumption should be that scanning has already happened. Even where exploitation has not been publicly observed, scanning for the vulnerable fingerprint is cheap and routine. Patching closes the door; log review and credential rotation close out the rest of the response.

Am I affected?

You are affected if your installation matches any of these version ranges:

Check your installed version against the list above. If you cannot determine the version, treat the system as affected and follow the upgrade path below.

Open bolo-solo's About dialog or run the vendor-documented version-check command. Compare the result against the affected ranges in the advisory.

How to fix CVE-2026-1813

  1. Read the vendor advisory in full: https://vuldb.com/?id.343981
  2. Upgrade bolo-solo to the patched build listed in the vendor advisory.
  3. Back up the configuration (and database, where applicable) before upgrading.
  4. Apply the patch in a maintenance window. For HA pairs, upgrade the standby node first, fail over, then upgrade the former primary.
  5. Restart the affected service so the patched binary loads, then verify the new version (see verification section).

npm / Yarn / pnpm


# Confirm the patched build against the vendor advisory: https://vuldb.com/?id.343981
# Update to the patched release <patched-version-from-advisory>.
npm install bolo-solo@<patched-version-from-advisory>
# Alternative pinning:
npm install bolo-solo@latest
npm ls bolo-solo

PyPI (pip / Poetry)


# Confirm the patched build against the vendor advisory: https://vuldb.com/?id.343981
pip install --upgrade "bolo-solo==<patched-version-from-advisory>"
pip show bolo-solo | grep -i version

# Poetry equivalent:
poetry add bolo-solo@<patched-version-from-advisory>

Docker / container


# Confirm the patched build against the vendor advisory: https://vuldb.com/?id.343981
docker pull <your-registry>/bolo-solo:<patched-version-from-advisory>
docker stop <app> && docker rm <app>
docker run -d --name <app> <your-registry>/bolo-solo:<patched-version-from-advisory>
docker image inspect <your-registry>/bolo-solo:<patched-version-from-advisory> --format '{{.Id}}'

Ubuntu / Debian


# Confirm the patched build against the vendor advisory: https://vuldb.com/?id.343981
sudo apt-get update
sudo apt-get install --only-upgrade openjdk-17-jdk
dpkg -s openjdk-17-jdk | grep -i version
# Target patched version: <patched-version>

RHEL / Rocky / AlmaLinux / Fedora


# Confirm the patched build against the vendor advisory: https://vuldb.com/?id.343981
sudo dnf upgrade --refresh openjdk-17-jdk -y
rpm -q openjdk-17-jdk
# Target patched version: <patched-version>

openSUSE


sudo zypper refresh
sudo zypper update openjdk-17-jdk

Verify the fix landed


# Confirm the patched build against the vendor advisory: https://vuldb.com/?id.343981
# 1. Confirm the running version equals the advisory's fixed-in build.
#    (Use the platform-specific version probe from the commands above.)

# 2. Re-scan with your vulnerability scanner (Nessus, Qualys, Tenable, OpenVAS).
#    The scanner should no longer flag CVE-2026-1813 on the patched target.

# 3. Inspect recent service and kernel logs for crash-loops or rollback events.
journalctl --since "10 minutes ago" | tail -200
dmesg --since "10 minutes ago" | tail -100

If you cannot patch immediately

Restrict access to the management interface to trusted internal IP addresses only. Block public access at the firewall and require VPN for any remote administration. Apply the patch as soon as a maintenance window allows.

How to verify the fix worked

If your installation was internet-reachable during the disclosure window, treat log review as part of the remediation rather than an optional follow-up. Look for unexpected administrator accounts in bolo-solo, scheduled tasks or cron jobs you did not create, new files in web-accessible directories, and outbound connections to addresses not in your baseline. Suspicious requests to the vulnerable endpoint immediately followed by successful 200-class responses with unusually large bodies are a strong indicator of exploitation.

Frequently asked questions

Is CVE-2026-1813 being exploited in the wild?

Public exploitation has not been confirmed by CISA at the time of writing. Treat the patch as time-sensitive anyway; reports often lag actual abuse.

Will a WAF or IDS rule fully mitigate CVE-2026-1813?

No. Network-layer filters can reduce noise and slow opportunistic scanners, but they will not stop a determined attacker. The vendor patch is the only durable fix.

How long should I plan for the upgrade?

Typical vendor-documented upgrade windows for bolo-solo run from a few minutes to under an hour depending on cluster size. Test in a staging environment first and follow the vendor's documented HA upgrade order.

References

*This guide was assembled from the official vendor advisory, the NVD record, and the CISA KEV catalog entry on 2026-05-25. Always confirm against the vendor advisory before applying changes in production.*