# CVE-2026-71308: Lemur: Unchecked `replaces[]` lets any user silence notifications and hijack auto-rotation for arbitrary certificates

> Authenticated users can hijack certificate rotation and suppress notifications for arbitrary certificates due to missing permission checks on replacement objects.

- **Severity:** High 8.1 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Any signed-in user
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 18 Aug 2026
- **Updated:** 18 Aug 2026
- **Also known as:** GHSA-cfh6-pv5c-38jv, PYSEC-2026-3675

## What is CVE-2026-71308?

CVE-2026-71308 is a high-severity missing authorization vulnerability in Netflix lemur, published on 18 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.

### Official description

Lemur manages TLS certificate creation. From 0.5.0 until 1.9.3, certificate create, upload, and edit requests accepted replaces[] or replacements identifiers that AssociatedCertificateSchema resolved with fetch_objects without a CertificatePermission check. Assigning those objects to Certificate.replaces invoked an append listener that disabled the victim certificate notifications and marked it as replaced. The victim was then excluded from get_all_pending_reissue, and certificate_rotate could deploy the attacker certificate to endpoints serving the victim. An authenticated non-read-only user could target certificates for which the user had no ownership or role, suppress lifecycle automation, and cause fleet-wide TLS disruption or unauthorized substitution. The fix authorizes every referenced replacement certificate before mutation. This issue is fixed in version 1.9.3.

Weakness: CWE-862 (Missing Authorization), CWE-639 (Authorization Bypass Through User-Controlled Key)

## Which versions are affected by CVE-2026-71308?

3 open source packages ship an affected version, including lemur.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `lemur` | PyPI | From 0.5.0 | 1.9.3 |
| `lemur` | PyPI | From 0.5.0 | 1.9.3 |
| `lemur` | PyPI | From 0.5.0 | 1.9.3 |

## How do I fix CVE-2026-71308?

Upgrade lemur to 1.9.3 or later.

## Is CVE-2026-71308 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-71308 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-71308 and fix it if it is affected.

What it is: CVE-2026-71308 is a high-severity missing authorization vulnerability in Netflix lemur, published on 18 Aug 2026. Any signed-in user can exploit it over the network, with no action from the victim.
Exploitation: It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-71308 exists.

Affected packages and fixed versions:
- lemur (PyPI): affected from 0.5.0; fixed in 1.9.3
- lemur (PyPI): affected from 0.5.0; fixed in 1.9.3
- lemur (PyPI): affected from 0.5.0; fixed in 1.9.3

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-2026-71308/ (Markdown: https://insights.sbomify.com/CVE-2026-71308/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-71308
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-71308
- OSV: https://osv.dev/vulnerability/CVE-2026-71308

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-71308/
Summaries are generated and may contain mistakes; the official description above is the record.