CVE-2025-65849
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedA 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.”
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · moderate confidenceThe Altcha Proof-of-Work obfuscation mechanism in versions 0.8.0+ contains a mathematical flaw that allows attackers to recover the PoW nonce in constant time through cryptanalysis, bypassing the intended anti-bot protection. This breaks the obfuscation layer by enabling deterministic derivation of values that were meant to require computational work to discover.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- High
- Integrity
- High
- Availability
- None
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Identify Altcha installationSearch for Altcha in project dependencies (package.json, requirements.txt, pom.xml, Gemfile, go.mod), installed npm packages, Python packages, or server-side libraries. Also check for Altcha client-side scripts or server-side modules.Affected if Altcha library or module is present in the environment
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Determine Altcha versionRun version check command appropriate to your package manager: npm list altcha, pip show altcha, composer show altcha, or inspect the version in your lockfile or dependency manifest.Affected if Installed version is 0.8.0 or higher (any 0.8.x, 0.9.x, etc.)
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Verify PoW feature is enabledExamine your Altcha configuration or initialization code for settings related to proof-of-work (pow: true, enablePoW, PoWMode, challengeType: 'pow', or similar). Check if Altcha is initialized with PoW challenge generation.Affected if The PoW/proof-of-work feature is actively enabled in the Altcha configuration or integration code
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Check for security-sensitive usageReview where Altcha PoW is deployed: login forms, API rate limiting, registration, password reset, or other security-critical endpoints. Note if it's used for anti-bot protection on sensitive operations.Affected if Altcha PoW is protecting security-sensitive endpoints or used as more than casual anti-bot deterrence (e.g., not just comment spam prevention)
You are affected if Altcha version 0.8.0 or higher is installed AND the PoW feature is enabled in your configuration, especially for security-sensitive purposes.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
From vendor dataOrganizations using Altcha PoW for security-sensitive purposes should replace it with proper cryptographic mechanisms; if used only for anti-bot deterrence, assess whether the documented limitations are acceptable for the threat model. Consider alternative bot-detection or rate-limiting solutions if stronger protection is required.
- Consultation4.0 h
- Implementation8.0 h
- Testing6.0 h
- Review / QA2.0 h
An estimate, not a bill — we confirm scope with you before any work starts. Need it this week? Rush from $5,600.
Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2025-65849 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2025-65849 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Verified mitigations, workarounds, and config changes
- Version or environment caveats, and links to real fixes
- No weaponised exploit code, or anything meant to cause harm
- No spam, self-promotion, credentials, or personal data