GHSA-6gvq-jcmp-8959
MEDIUMALTCHA Proof-of-Work Vulnerable to Challenge Splicing and Replay
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
github.com/altcha-org/altcha-lib-go💧altcha☕org.altcha:altcha📦altcha-lib🐘altcha-org/altcha🐍altcha💎altchaReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go, Hex, Maven packages — download data is not available via public APIs for these ecosystems.
Description
Impact
A cryptographic semantic binding flaw in ALTCHA libraries allows challenge payload splicing, which may enable replay attacks. The HMAC signature does not unambiguously bind challenge parameters to the nonce, allowing an attacker to reinterpret a valid proof-of-work submission with a modified expiration value. This may allow previously solved challenges to be reused beyond their intended lifetime, depending on server-side replay handling and deployment assumptions.
The vulnerability primarily impacts abuse-prevention mechanisms such as rate limiting and bot mitigation. It does not directly affect data confidentiality or integrity.
Patches
This issue has been addressed by enforcing explicit semantic separation between challenge parameters and the nonce during HMAC computation.
Users are advised to upgrade to patched versions.
Workarounds
As a mitigation, implementations may append a delimiter to the end of the salt value prior to HMAC computation (for example, <salt>?expires=<time>&). This prevents ambiguity between parameters and the nonce and is backward-compatible with existing implementations, as the delimiter is treated as a standard URL parameter separator.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐹Go | github.com/altcha-org/altcha-lib-go | all versions | 1.0.0 |
| 💧Hex | altcha | all versions | 1.0.0 |
| ☕Maven | org.altcha:altcha | all versions | 1.3.0 |
| 📦npm | altcha-lib | all versions | 1.4.1 |
| 🐘Packagist | altcha-org/altcha | all versions | 1.3.1 |
| 🐍PyPI | altcha | all versions | 1.0.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/altcha-org/altcha-lib-go. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update github.com/altcha-org/altcha-lib-go to 1.0.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-6gvq-jcmp-8959 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-6gvq-jcmp-8959 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-6gvq-jcmp-8959. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-6gvq-jcmp-8959 in your dependencies?
O3 detects GHSA-6gvq-jcmp-8959 across Go, Hex, Maven dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.