# CVE-2026-48797: Backpropagate: backprop ui --auth and backprop ui --share do not enforce authentication > Attackers can access the web UI without authentication to read datasets, trigger training, and push to HuggingFace Hub when using specific CLI flags. - **Severity:** Critical 9.3 (`CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:H/VI:H/VA:H/SC:N/SI:N/SA:N`) - **Exploited in the wild:** Not known - **Login needed:** Not needed - **Attackable:** Over the internet - **Victim action needed:** Not needed - **Fix available:** Yes - **Published:** 16 Jun 2026 - **Updated:** 18 Jun 2026 - **Also known as:** GHSA-f65r-h4g3-3h9h, PYSEC-2026-291 ## What is CVE-2026-48797? CVE-2026-48797 is a critical missing authorization vulnerability in mcp-tool-shop-org @mcptoolshop/backpropagate, published on 16 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. ### Official description 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 BACKPROPAGATE_UI_AUTH=user:pass to the subprocess that launches the Reflex backend. The Reflex backend (backpropagate/ui_app/**) never reads BACKPROPAGATE_UI_AUTH. 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, SHIP_GATE) 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. Weakness: CWE-862 (Missing Authorization), CWE-358 (Improperly Implemented Security Check for Standard), CWE-1295 (Debug Messages Revealing Unnecessary Information) ## Which versions are affected by CVE-2026-48797? 5 open source packages ship an affected version, including @mcptoolshop/backpropagate and backpropagate. | Package | Ecosystem | Affected | Fixed in | | --- | --- | --- | --- | | `@mcptoolshop/backpropagate` | npm | From 1.1.0 | 1.2.0 | | `@mcptoolshop/backpropagate` | npm | From 1.1.0 | 1.2.0 | | `backpropagate` | PyPI | From 1.1.0 | 1.2.0 | | `backpropagate` | PyPI | From 1.1.0 | 1.2.0 | | `backpropagate` | PyPI | From 1.1.0 | 1.2.0 | ## How do I fix CVE-2026-48797? Upgrade @mcptoolshop/backpropagate to 1.2.0 or later. ## Is CVE-2026-48797 being exploited? There is no known exploitation of CVE-2026-48797 in the wild and no public exploit code. ## Fix prompt for AI coding agents ```text Check this codebase for CVE-2026-48797 and fix it if it is affected. What it is: CVE-2026-48797 is a critical missing authorization vulnerability in mcp-tool-shop-org @mcptoolshop/backpropagate, published on 16 Jun 2026. An attacker can exploit it over the internet without logging in, with no action from the victim. Exploitation: There is no known exploitation of CVE-2026-48797 in the wild and no public exploit code. Affected packages and fixed versions: - @mcptoolshop/backpropagate (npm): affected from 1.1.0; fixed in 1.2.0 - @mcptoolshop/backpropagate (npm): affected from 1.1.0; fixed in 1.2.0 - backpropagate (PyPI): affected from 1.1.0; fixed in 1.2.0 - backpropagate (PyPI): affected from 1.1.0; fixed in 1.2.0 - backpropagate (PyPI): affected from 1.1.0; fixed in 1.2.0 Task: 1. Search the dependency manifests and lockfiles (for example package.json, package-lock.json, requirements.txt, poetry.lock, uv.lock, pom.xml, build.gradle, go.mod, Cargo.lock, Gemfile.lock) and any Dockerfiles for the affected packages, including transitive dependencies. 2. If an affected version is in use, upgrade it to the fixed version for its release line with the project's package manager, so the lockfile is regenerated. Prefer the smallest upgrade that fixes it. 3. If there is no fix, or the upgrade would break the build, do not guess: explain the risk and the safest workaround instead. 4. Run the tests and summarise what changed and why. 5. If nothing in the project is affected, say so and change nothing. Reference: https://insights.sbomify.com/CVE-2026-48797/ (Markdown: https://insights.sbomify.com/CVE-2026-48797/index.md) ``` ## Sources - CVE record: https://www.cve.org/CVERecord?id=CVE-2026-48797 - NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-48797 - OSV: https://osv.dev/vulnerability/CVE-2026-48797 --- From sbomify Insights: https://insights.sbomify.com/CVE-2026-48797/ Summaries are generated and may contain mistakes; the official description above is the record.