{"cve":"CVE-2025-68113","nvd":{"published":"2025-12-16T01:15:53.383","modified":"2026-10-07T19:10:00.160","status":"Deferred","description":"ALTCHA is privacy-first software for captcha and bot protection. 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. 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, which include version 1.0.0 of the altcha Golang package, version 1.0.0 of the altcha Rubygem, version 1.0.0 of the altcha pip package, version 1.0.0 of the altcha Erlang package, version 1.4.1 of the altcha-lib npm package, version 1.3.1 of the altcha-org/altcha Composer package, and version 1.3.0 of the org.altcha:altcha Maven package. 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.","cvss_v4":null,"cvss_v3":{"version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:L/A:L","score":6.5},"cwes":["CWE-115","CWE-347"],"references":["https://github.com/altcha-org/altcha-lib-ex/commit/09b2bad466ad0338a5b24245380950ea9918333e","https://github.com/altcha-org/altcha-lib-go/commit/4a5610745ef79895a67bac858b2e4f291c2614b8","https://github.com/altcha-org/altcha-lib-java/commit/69277651fdd6418ae10bf3a088901506f9c62114","https://github.com/altcha-org/altcha-lib-java/releases/tag/v1.3.0","https://github.com/altcha-org/altcha-lib-php/commit/9e9e70c864a9db960d071c77c778be0c9ff1a4d0"],"products":[],"source":"nvd","synced_at":"2026-10-19T22:17:07.138532058+00:00"},"epss":{"cve":"CVE-2025-68113","score":0.00463,"percentile":0.39832,"date":"2026-10-25"},"kev":null,"osv":[{"id":"GHSA-6gvq-jcmp-8959","url":"https://osv.dev/vulnerability/GHSA-6gvq-jcmp-8959","summary":"ALTCHA Proof-of-Work Vulnerable to Challenge Splicing and Replay","modified":"2026-09-10T03:50:31.591423196Z","packages":[{"ecosystem":"npm","name":"altcha-lib","purl":"pkg:npm/altcha-lib","ranges":["<1.4.1"],"fixed":["1.4.1"]},{"ecosystem":"Packagist","name":"altcha-org/altcha","purl":"pkg:composer/altcha-org/altcha","ranges":["<1.3.1"],"fixed":["1.3.1"]},{"ecosystem":"Go","name":"github.com/altcha-org/altcha-lib-go","purl":"pkg:golang/github.com/altcha-org/altcha-lib-go","ranges":["<1.0.0"],"fixed":["1.0.0"]},{"ecosystem":"Maven","name":"org.altcha:altcha","purl":"pkg:maven/org.altcha/altcha","ranges":["<1.3.0"],"fixed":["1.3.0"]},{"ecosystem":"RubyGems","name":"altcha","purl":"pkg:gem/altcha","ranges":["<1.0.0"],"fixed":["1.0.0"]},{"ecosystem":"PyPI","name":"altcha","purl":"pkg:pypi/altcha","ranges":["<1.0.0"],"fixed":["1.0.0"]},{"ecosystem":"Hex","name":"altcha","purl":"pkg:hex/altcha","ranges":["<1.0.0"],"fixed":["1.0.0"]}]},{"id":"GO-2025-4239","url":"https://osv.dev/vulnerability/GO-2025-4239","summary":"ALTCHA Proof-of-Work Vulnerable to Challenge Splicing and Replay in github.com/altcha-org/altcha-lib-go","modified":"2026-07-07T17:56:08.392027300Z","packages":[{"ecosystem":"Go","name":"github.com/altcha-org/altcha-lib-go","purl":"pkg:golang/github.com/altcha-org/altcha-lib-go","ranges":["<1.0.0"],"fixed":["1.0.0"]}]},{"id":"PYSEC-2026-1115","url":"https://osv.dev/vulnerability/PYSEC-2026-1115","summary":"ALTCHA Proof-of-Work Vulnerable to Challenge Splicing and Replay","modified":"2026-07-07T17:56:08.392027300Z","packages":[{"ecosystem":"PyPI","name":"altcha","purl":"pkg:pypi/altcha","ranges":["<1.0.0"],"fixed":["1.0.0"]}]}],"attribution":["This product uses the NVD API but is not endorsed or certified by the NVD.","EPSS scores: FIRST Exploit Prediction Scoring System, https://www.first.org/epss","Known exploited vulnerabilities: CISA Known Exploited Vulnerabilities Catalog, https://www.cisa.gov/known-exploited-vulnerabilities-catalog","Package advisories: OSV (https://osv.dev), from the GitHub Advisory Database, PyPA, Go, RustSec and other ecosystem databases, under CC-BY 4.0 or CC0","CVE records: the CVE Program's CVE List (https://www.cve.org), under its terms of use (https://www.cve.org/Legal/TermsOfUse). CVE is a registered trademark of The MITRE Corporation; this product is not affiliated with the CVE Program."]}