# CVE-2026-26999: Traefik: tcp router clears read deadlines before tls forwarding, enabling stalled handshakes (slowloris doS)

> Remote attackers can exhaust resources by stalling TLS handshakes on TCP routers, causing denial of service for all services on the entrypoint.

- **Severity:** High 7.5 (`CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** Not needed
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 5 Mar 2026
- **Updated:** 15 Jul 2026
- **Also known as:** CLEANSTART-2026-DR86429, GHSA-xw98-5q62-jx94, GO-2026-4594, MINI-47qm-c4mv-r93x, MINI-rp72-qv6p-cfx5

## What is CVE-2026-26999?

CVE-2026-26999 is a high-severity denial of service vulnerability in Traefik Traefik, published on 5 Mar 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Traefik is an HTTP reverse proxy and load balancer. Prior to versions 2.11.38 and 3.6.9, there is a potential vulnerability in Traefik managing TLS handshake on TCP routers. When Traefik processes a TLS connection on a TCP router, the read deadline used to bound protocol sniffing is cleared before the TLS handshake is completed. When a TLS handshake read error occurs, the code attempts a second handshake with different connection parameters, silently ignoring the initial error. A remote unauthenticated client can exploit this by sending an incomplete TLS record and stopping further data transmission, causing the TLS handshake to stall indefinitely and holding connections open. By opening many such stalled connections in parallel, an attacker can exhaust file descriptors and goroutines, degrading availability of all services on the affected entrypoint. This issue has been patched in versions 2.11.38 and 3.6.9.

Weakness: CWE-772 (Missing Release of Resource after Effective Lifetime), CWE-400 (Uncontrolled Resource Consumption)

## Which versions are affected by CVE-2026-26999?

7 open source packages ship an affected version, including github.com/traefik/traefik/v2, github.com/traefik/traefik and github.com/traefik/traefik/v3. It affects 1 product.


| Package | Ecosystem | Affected | Fixed in |
| --- | --- | --- | --- |
| `github.com/traefik/traefik/v2` | Go | All versions | 2.11.38 |
| `github.com/traefik/traefik/v2` | Go | All versions | 2.11.38 |
| `github.com/traefik/traefik/v2` | Go | All versions | 2.11.38 |
| `github.com/traefik/traefik` | Go | All versions | None |
| `github.com/traefik/traefik/v3` | Go | All versions | 3.6.9 |
| `github.com/traefik/traefik/v3` | Go | All versions | 3.6.9 |
| `github.com/traefik/traefik/v3` | Go | All versions | 3.6.9 |

Products: Traefik Traefik.

## How do I fix CVE-2026-26999?

Upgrade github.com/traefik/traefik/v2 to 2.11.38 or later.

## Is CVE-2026-26999 being exploited?

There is no known exploitation of CVE-2026-26999 in the wild and no public exploit code.

## Other vulnerabilities in Traefik Traefik

- [CVE-2024-45410](https://insights.sbomify.com/CVE-2024-45410/): HTTP client can remove the X-Forwarded headers in Traefik (critical 9.8)
- [CVE-2026-88877](https://insights.sbomify.com/CVE-2026-88877/): Traefik v3.7.0 Authentication Bypass via from-to-www-redirect (critical 9.3)
- [CVE-2026-85595](https://insights.sbomify.com/CVE-2026-85595/): Traefik before v2.11.55 and v3.0.0 through v3.7.10 Authentication Bypass via digestAuth (critical 9.3)
- [CVE-2026-88007](https://insights.sbomify.com/CVE-2026-88007/): Traefik HTTP/3 Backend NTLM Connection Reuse (critical 9.1)
- [CVE-2026-88009](https://insights.sbomify.com/CVE-2026-88009/): Traefik: Rootless HTTP/1 request-target routes as "/" but is forwarded verbatim, bypassing path-scoped routing, middleware guards and access logging (high 8.8)

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-26999 and fix it if it is affected.

What it is: CVE-2026-26999 is a high-severity denial of service vulnerability in Traefik Traefik, published on 5 Mar 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-2026-26999 in the wild and no public exploit code.

Affected packages and fixed versions:
- github.com/traefik/traefik/v2 (Go): affected all versions; fixed in 2.11.38
- github.com/traefik/traefik/v2 (Go): affected all versions; fixed in 2.11.38
- github.com/traefik/traefik/v2 (Go): affected all versions; fixed in 2.11.38
- github.com/traefik/traefik (Go): affected all versions; no fix listed
- github.com/traefik/traefik/v3 (Go): affected all versions; fixed in 3.6.9
- github.com/traefik/traefik/v3 (Go): affected all versions; fixed in 3.6.9
- github.com/traefik/traefik/v3 (Go): affected all versions; fixed in 3.6.9

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-2026-26999/ (Markdown: https://insights.sbomify.com/CVE-2026-26999/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-26999
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-26999
- OSV: https://osv.dev/vulnerability/CVE-2026-26999

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-26999/
Summaries are generated and may contain mistakes; the official description above is the record.