# CVE-2026-70409: eldap does not bound the port component of a referral URL before integer conversion

> A malicious LDAP server can cause denial of service in Erlang applications by sending referral URLs with excessively long port numbers, triggering expensive integer conversions.

- **Severity:** Medium 6.3 (`CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:L/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:** 1 Sep 2026
- **Updated:** 8 Sep 2026
- **Also known as:** AZL-98475, DEBIAN-CVE-2026-70409, EEF-CVE-2026-70409, GHSA-9vgh-c8cm-m9p4, UBUNTU-CVE-2026-70409

## What is CVE-2026-70409?

CVE-2026-70409 is a medium-severity denial of service vulnerability in Erlang OTP, published on 1 Sep 2026. An attacker can exploit it over the internet without logging in, with no action from the victim.

### Official description

Improper Validation of Specified Quantity in Input vulnerability in Erlang/OTP eldap allows a malicious or compromised LDAP server to degrade availability by returning a referral URL whose port component is a very long run of digits.

eldap:parse_port/2 passes the port substring straight to list_to_integer/1 with no length bound. The surrounding try ... catch only rejects a value that fails to parse, so a syntactically valid port of up to roughly 1.26 million digits converts successfully and costs the caller hundreds of milliseconds of arbitrary-precision arithmetic per referral. The conversion function itself is documented to accept integers of any size, so bounding the input is the caller's responsibility. Reaching the flaw requires the application to pass a server-supplied referral to eldap:parse_ldap_url/1, which eldap never calls itself: referral strings are returned to the caller unparsed.

This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, from OTP 28.0 before OTP 28.5.0.6, and from OTP 29.0 before OTP 29.0.6, corresponding to eldap from 1.0.3 before 1.2.14.2, from 1.2.15 before 1.2.16.1, and from 1.3 before 1.3.1.

Weakness: CWE-1284 (Improper Validation of Specified Quantity in Input)

## Which versions are affected by CVE-2026-70409?


## How do I fix CVE-2026-70409?

Upgrade to a fixed version.

## Is CVE-2026-70409 being exploited?

There is no known exploitation of CVE-2026-70409 in the wild and no public exploit code.

## Fix prompt for AI coding agents

```text
Check this codebase for CVE-2026-70409 and fix it if it is affected.

What it is: CVE-2026-70409 is a medium-severity denial of service vulnerability in Erlang OTP, published on 1 Sep 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-2026-70409 in the wild and no public exploit code.

Affected product: Erlang OTP. No package-level version data is available, so check the vendor advisory linked from the reference page.

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-2026-70409/ (Markdown: https://insights.sbomify.com/CVE-2026-70409/index.md)
```

## Sources

- CVE record: https://www.cve.org/CVERecord?id=CVE-2026-70409
- NVD: https://nvd.nist.gov/vuln/detail/CVE-2026-70409
- OSV: https://osv.dev/vulnerability/CVE-2026-70409

---
From sbomify Insights: https://insights.sbomify.com/CVE-2026-70409/
Summaries are generated and may contain mistakes; the official description above is the record.