# CVE-2026-70667: Lemur: SSRF protection in certificate revocation checking bypassable via HTTP redirects and DNS rebinding (incomplete fix for GHSA-54vg-pfh7-jq95)

> Attackers can bypass SSRF protections in Lemur's certificate revocation checks via redirects and DNS rebinding to access internal resources.

- **Severity:** Medium 6.3 (`CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:L/I:L/A:L`)
- **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:** 19 Aug 2026
- **Also known as:** GHSA-f3qq-49m6-rw8f, PYSEC-2026-3676

## What is CVE-2026-70667?

CVE-2026-70667 is a medium-severity server-side request forgery 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. Prior to 1.9.3, _validate_revocation_url in lemur/certificates/verify.py checked the original CRL or OCSP URL but the later request could reach a different destination. The CRL requests.get call followed HTTP redirects without validating each Location target, so a public attacker-controlled URL could redirect to loopback, RFC1918, link-local, or instance-metadata addresses. Validation and connection also performed separate DNS resolutions, creating a time-of-check time-of-use window for DNS rebinding on both CRL and OCSP paths. An operator uploading a certificate through POST /api/1/certificates/upload could therefore induce blind internal requests despite the earlier mitigation. The fix disables redirects and pins validated addresses while preserving the correct Host value. This issue is fixed in version 1.9.3.

Weakness: CWE-918 (Server-Side Request Forgery), CWE-367 (Time-of-check Time-of-use (TOCTOU) Race Condition)

## Which versions are affected by CVE-2026-70667?

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


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `lemur` | PyPI | All versions | 1.9.3 |
| `lemur` | PyPI | All versions | 1.9.3 |
| `lemur` | PyPI | All versions | 1.9.3 |

## How do I fix CVE-2026-70667?

Upgrade lemur to 1.9.3 or later.

## Is CVE-2026-70667 being exploited?

It is not confirmed as exploited in the wild, but public exploit code for CVE-2026-70667 exists.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-70667 and fix it if it is affected.

What it is: CVE-2026-70667 is a medium-severity server-side request forgery 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-2026-70667 exists.

Affected packages and fixed versions:
- lemur (PyPI): affected all versions; fixed in 1.9.3
- lemur (PyPI): affected all versions; fixed in 1.9.3
- lemur (PyPI): affected all versions; 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-2026-70667/ (Markdown: https://insights.sbomify.com/CVE-2026-70667/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-70667
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-70667
- OSV: https://osv.dev/vulnerability/CVE-2026-70667

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-70667/
Summaries are generated and may contain mistakes; the official description above is the record.