# CVE-2026-26998: Traefik: unbounded io.ReadAll on auth server response body causes OOM denial of service(DOS)

> Traefik crashes with out-of-memory errors when ForwardAuth middleware receives unbounded responses from authentication servers.

- **Severity:** Medium 4.4 (`CVSS:3.1/AV:N/AC:H/PR:H/UI:N/S:U/C:N/I:N/A:H`)
- **Exploited in the wild:** Not known
- **Login needed:** An administrator
- **Attackable:** Over the internet
- **Victim action needed:** Not needed
- **Fix available:** Yes
- **Published:** 5 Mar 2026
- **Updated:** 6 Mar 2026
- **Also known as:** CLEANSTART-2026-IZ44500, GHSA-fw45-f5q2-2p4x, GO-2026-4593, MINI-4m5f-552h-3v8m, MINI-xh7v-j27j-rw8w

## What is CVE-2026-26998?

CVE-2026-26998 is a medium-severity denial of service vulnerability in Traefik Traefik, published on 5 Mar 2026. An attacker needs administrator access to exploit it, 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 the ForwardAuth middleware responses. When Traefik is configured to use the ForwardAuth middleware, the response body from the authentication server is read entirely into memory without any size limit. There is no maxResponseBodySize configuration to restrict the amount of data read from the authentication server response. If the authentication server returns an unexpectedly large or unbounded response body, Traefik will allocate unlimited memory, potentially causing an out-of-memory (OOM) condition that crashes the process. This results in a denial of service for all routes served by the affected Traefik instance. This issue has been patched in versions 2.11.38 and 3.6.9.

Weakness: CWE-770 (Allocation of Resources Without Limits or Throttling)

## Which versions are affected by CVE-2026-26998?

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-2026-26998?

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

## Is CVE-2026-26998 being exploited?

There is no known exploitation of CVE-2026-26998 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-2026-26998 and fix it if it is affected.

What it is: CVE-2026-26998 is a medium-severity denial of service vulnerability in Traefik Traefik, published on 5 Mar 2026. An attacker needs administrator access to exploit it, with no action from the victim.
Exploitation: There is no known exploitation of CVE-2026-26998 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-2026-26998/ (Markdown: https://insights.sbomify.com/CVE-2026-26998/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-26998
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-26998
- OSV: https://osv.dev/vulnerability/CVE-2026-26998

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-26998/
Summaries are generated and may contain mistakes; the official description above is the record.