CVE-2025-65849 Altcha Proof-of-Work obfuscation mode cryptanalytic break
Attackers can bypass Altcha Proof-of-Work obfuscation to recover nonces, defeating bot protection mechanisms in npm packages.
- Exploited in the wild
- Not known
- Login needed
- Not needed
- Attackable
- Over the internet
- Victim action needed
- Not needed
- Fix
- None listed
What is CVE-2025-65849?
CVE-2025-65849 is a critical vulnerability in n/a, published on 8 Dec 2025. An attacker can exploit it over the internet without logging in, with no action from the victim.
Official description
A cryptanalytic break in Altcha Proof-of-Work obfuscation mode version 0.8.0 and later allows for remote visitors to recover the Proof-of-Work nonce in constant time via mathematical deduction. NOTE: this is disputed by the Supplier because the product's objective is "to discourage automated scraping / bots, not guarantee resistance to determined attackers." The documentation states “the goal is not to provide a secure cryptographic algorithm but to use a proof-of-work mechanism that allows any capable device to decrypt the hidden data.”
Weakness: CWE-327
Which versions are affected by CVE-2025-65849?
2 open source packages ship an affected version, including altcha.
| Package | Affected | Fixed in |
|---|---|---|
altcha npm | From 0.8.0 to 2.2.4 | None |
altcha npm | From 0.8.0 to 2.2.4 | None |
How do I fix CVE-2025-65849?
No fix has been published for CVE-2025-65849 yet. Limit exposure of the affected software until one is available.
Is CVE-2025-65849 being exploited?
There is no known exploitation of CVE-2025-65849 in the wild and no public exploit code.
Sources
Also known as GHSA-mpmc-qchh-r9q8.