CVE-2026-123660vulnerability-lookup uncontrolled recursion
CVE-2026-123660 is a uncontrolled recursion in vulnerability-lookup, rated medium (5.3 on CVSS 4.0).
Why this priority: Medium severity, with no exploitation signal.
Published · Updated · NVD status: Received
What it is
Deeply nested input drives recursion until the process crashes. Resources are allocated without a cap, so a caller can exhaust them.
How it is reached
An attacker can exploit it over the network, with an ordinary user account, and nobody has to click anything.
What an attacker gains
The direct impact is limited: partial access to data or a partial outage. In practice, this kind of flaw lets an attacker exhaust CPU, memory or connections until the service stops answering.
Is it being exploited?
There is no public report of exploitation yet.
What to do
- Upgrade vulnerability-lookup to 6.4.1 or later.
- Until it is patched, review who holds accounts that can reach it.
Description from NVD
In Vulnerability-Lookup 5.5.1 up to but not including 6.4.1, a signed-in user could make the server allocate memory far out of proportion to their input through a webhook notification's payload template. Each placeholder's format specifier was passed unchanged to Python's string formatting, which builds the padded result before its size can be checked. A template of a few dozen bytes, such as {"text": "{title:>999999999}"}, therefore produced a string of about 1 GB when the notification form test-rendered it on save, and repeating such fields multiplied the cost. Templates that passed the save check could also repeat placeholders such as {text} thousands of times; the notification daemon rebuilt those on every webhook delivery. Deeply nested templates raised an unhandled recursion error (HTTP 500). An attacker needs only an account, which the default configuration lets anyone create after e-mail confirmation. They could exhaust the memory of web workers or the notification daemon, causing a denial of service. Version 6.4.1 caps every number in a format specifier at 256, limits a rendered template to 1,000,000 characters both on save and at delivery, and rejects templates nested deeper than 32 levels.
What this means for your architecture.
A CVE names a product. Whether it matters depends on where that product sits in your systems: what reaches it, which trust boundary it guards and what it can reach once compromised. Veriom maps your components, their relationships and your trust boundaries from your code, cloud and delivery evidence, so you can see where a component like this sits. The radar itself does not look at your systems.
Components it touches
- Public entry points and shared services that must stay up. The flaw sits between untrusted traffic and shared capacity.
- Interfaces that accept external input. The flaw sits at the input boundary of the affected component.
Trust boundaries in play
- Authenticated network access. An account is needed, so exposure follows who can sign in: customers, partners or staff.
- Between untrusted traffic and shared capacity. An attacker who crosses it can exhaust CPU, memory or connections until the service stops answering.
- At the input boundary of the affected component. An attacker who crosses it can drive the component into behaviour its authors did not intend.
Questions to answer about your own systems
- Where does vulnerability-lookup run in your systems, and at which version?
- Which of those instances can be reached from the internet or partner networks?
- What can it reach once compromised: which data stores, secrets and services?
Read more
Sources
- CVE records and CVSS scores from the NVD CVE API. This product uses the NVD API but is not endorsed or certified by the NVD.
- Exploitation status from CISA’s Known Exploited Vulnerabilities catalog.
- Exploit likelihood from FIRST’s Exploit Prediction Scoring System (EPSS), refreshed daily.
- Explanations are written by Veriom from fixed templates over each record’s data, not by a person reviewing each CVE. Descriptions are quoted from the records as published.