CVE-2021-41168 Hash-Collision Denial-of-Service Vulnerability in snudown
An attacker can cause denial of service in snudown by exploiting weak hash functions in its reference table implementation.
- Exploited in the wild
- Not known
- Login needed
- Any signed-in user
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2021-41168?
CVE-2021-41168 is a medium-severity denial of service vulnerability in reddit snudown, published on 21 Oct 2021. Any signed-in user can exploit it over the network, with no action from the victim.
Official description
Snudown is a reddit-specific fork of the Sundown Markdown parser used by GitHub, with Python integration added. In affected versions snudown was found to be vulnerable to denial of service attacks to its reference table implementation. References written in markdown ` [reference_name]: https://www.example.com` are inserted into a hash table which was found to have a weak hash function, meaning that an attacker can reliably generate a large number of collisions for it. This makes the hash table vulnerable to a hash-collision DoS attack, a type of algorithmic complexity attack. Further the hash table allowed for duplicate entries resulting in long retrieval times. Proofs of concept and further discussion of the hash collision issue are discussed on the snudown GHSA(https://github.com/reddit/snudown/security/advisories/GHSA-6gvv-9q92-w5f6). Users are advised to update to version 1.7.0.
Which versions are affected by CVE-2021-41168?
It affects 1 product.
Products include Reddit Snudown.
How do I fix CVE-2021-41168?
No fix has been published for CVE-2021-41168 yet. Limit exposure of the affected software until one is available.
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-2021-41168 being exploited?
There is no known exploitation of CVE-2021-41168 in the wild and no public exploit code.
Sources
Also known as GHSA-6gvv-9q92-w5f6.