CVE-2026-48797: Backpropagate: backprop ui --auth and backprop ui --share do not enforce authentication

Should you act?

Critical and remotely reachable

No known exploitation yet, but it is network-reachable without credentials. This signal is computed from CISA KEV, EPSS and CVSS data; it is not an editorial verdict.

• No confirmed exploitation. It is not in CISA’s KEV catalog and CISA’s SSVC assessment records no known exploitation. That can change quickly after a public write-up; re-check if you are affected.
• EPSS 0.6%, percentile 46: FIRST’s model estimates a 0.6% chance of exploitation activity in the next 30 days, higher than 46% of all scored CVEs (low). EPSS is a probability, not a verdict.
• Remotely reachable with no login and no user interaction. If the vulnerable service is exposed to the internet, prioritize it.
• Only applies if your dependency tree includes backpropagate (PyPI) >= 1.1.0, < 1.2.0, fixed in 1.2.0; @mcptoolshop/backpropagate (npm) >= 1.1.0, < 1.2.0, fixed in 1.2.0. Check your lockfile, including transitive dependencies.

What it is

Backpropagate is a Python library for fine-tuning large language models on a single GPU. In versions 1.1.0 and 1.1.1, the optional Reflex web UI exposes a training control plane without authentication: dataset upload, model load, training start/stop, multi-run orchestration, GGUF export, and HuggingFace Hub push. The CLI accepts two operator-facing flags intended as security controls: --auth user:pass — documented as "require HTTP Basic authentication on every request to the UI." and--share — documented as "expose the UI on a public address; requires --auth." When --auth user:pass is passed, the CLI prints Auth: enabled (user: ) to confirm to the operator that authentication is active, then exports BACKPROPAGATEUIAUTH=user:pass to the subprocess that launches the Reflex backend. The Reflex backend (backpropagate/uiapp/) never reads BACKPROPAGATEUIAUTH. No authentication middleware is registered. No request-level guard runs. No WebSocket upgrade guard runs. Any client that reaches the bound port — local or remote, depending on whether --share is used — has full UI access. An inline comment at backpropagate/cli.py:1217-1218 in the v1.1.0 source documents the gap: "For Phase 1 the variable is exported but Reflex doesn't read it yet." This comment was internal-facing; the user-facing documentation (README, CHANGELOG, SHIPGATE) advertised the contract as enforced. An attacker who reaches the bound port can read uploaded datasets, trigger arbitrary training runs against any local base models as well as read their paths, trigger HuggingFace Hub pushes and cause disk-fill DoS. This issue has been fixed in version 1.2.0. If developers cannot immediately upgrade to 1.2.0 run backprop ui with no flags so it binds to localhost, use SSH port-forwarding (ssh -L 7860:localhost:7860 ) instead of --share for remote access, and audit any host previously launched with --share, re-issuing any HF tokens used during those sessions.

From the GitHub advisory

Summary

In backpropagate >= 1.1.0, the optional Reflex web UI (pip install backpropagate[ui], launched via backprop ui) exposes a training control plane: dataset upload, model load, training start/stop, multi-run orchestration, GGUF export, and HuggingFace Hub push.

The CLI accepts two operator-facing flags intended as security controls:

- --auth user:pass — documented as "require HTTP Basic authentication on every request to the UI." - --share — documented as "expose the UI on a public address; requires --auth."

When --auth user:pass is passed, the CLI prints Auth: enabled (user: ) to confirm to the operator that authentication is active, then exports BACKPROPAGATEUIAUTH=user:pass to the subprocess that launches the Reflex backend.

Weakness type: CWE-358, CWE-862, CWE-1295.

Product: backpropagate (PyPI) · Assigned by: GitHub_M · Published: 2026-06-16

Affected and fixed versions

Severity scores

• Attack vector: network (remotely reachable)
• Attack complexity: low
• Attack requirements: none
• Privileges required: none (no login)
• User interaction: none

CVSS measures how bad a flaw is if exploited, not how likely exploitation is. Read it next to the exploitation data below.

Exploitation and urgency

• CISA KEV: not listed (no confirmed in-the-wild exploitation known to CISA).
• CISA SSVC assessment: exploitation none, automatable no, technical impact total.
• FIRST EPSS (model of 2026-10-21): 0.57% probability of exploitation activity in the next 30 days; percentile 46.

Timeline

• 2026-06-16 — CVE record published by GitHub_M
• 2026-06-18 — CVE record last updated
• 2026-06-26 — GitHub-reviewed advisory GHSA-f65r-h4g3-3h9h published (critical)

Sources and references

Original sources first. Version and fix details should always be confirmed against the vendor or project advisory.

Vulnerability records

1. GitHub Advisory GHSA-f65r-h4g3-3h9h github.com
2. CVE.org record CVE-2026-48797 cve.org
3. NVD entry CVE-2026-48797 nvd.nist.gov

Other references from the CVE record and advisory

1. github.com github.com
2. github.com github.com

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