CVE-2025-6703 transport/fc.rs: panic attempting to send MAX_DATA with value larger max varint
An attacker can cause a crash in the Mozilla neqo library by sending a MAX_DATA frame with an oversized value, leading to denial of service.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- A user has to click or open something
- Fix
- None listed
What is CVE-2025-6703?
CVE-2025-6703 is a low-severity denial of service vulnerability in Mozilla neqo, published on 26 Jun 2025. An attacker can exploit it over the internet without logging in, and only if a user opens a file or follows a link.
Official description
Improper Input Validation vulnerability in Mozilla neqo leads to an unexploitable crash..This issue affects neqo: from 0.4.24 through 0.13.2.
Weakness: CWE-20
Which versions are affected by CVE-2025-6703?
It affects 1 product.
Products include Mozilla Neqo.
How do I fix CVE-2025-6703?
No fix has been published for CVE-2025-6703 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-2025-6703 being exploited?
There is no known exploitation of CVE-2025-6703 in the wild and no public exploit code.
Sources
Also known as GHSA-jfv6-x22w-grhf.