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.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- Available
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
Which versions are affected by CVE-2026-70409?
How do I fix CVE-2026-70409?
Upgrade to a fixed version.
Upgrade, then put limits on request size, rate and nesting depth so one client cannot exhaust the service. More about Denial of service.
Is CVE-2026-70409 being exploited?
There is no known exploitation of CVE-2026-70409 in the wild and no public exploit code.
Sources
Also known as AZL-98475, DEBIAN-CVE-2026-70409, EEF-CVE-2026-70409, GHSA-9vgh-c8cm-m9p4, UBUNTU-CVE-2026-70409.