`CVE-2025-68113`

Severity	6.5 Medium CVSS 3.1
Fixed in	`1.3.0`
Weakness	CWE-115
Published	16 Dec 2025
Updated	7 Oct 2026

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.

CWE-347

Exploitation status

No public exploit

No exploit has been reported in the sources we check.

CISA KEV not listed
VulnCheck KEV not listed
CISA Vulnrichment exploitation: none
Indexed PoC none indexed
EPSS 0.46% chance in 30 days

Waratek protection

No exploit published

Within Waratek scope. In the sources we check, nobody has published exploit code for this CVE or reported it being exploited.

A public code fix exists: altcha-org/altcha-lib-ex 09b2bad.

Protection none
Action unverified
Review automated Upstream data
Record active

Decided by	Medium or Low severity, no CISA or VulnCheck KEV listing, no PoC clearing the evidence bar, no CISA verdict, no Oracle advisory
Finding	This CVE is MEDIUM severity, is not listed in CISA KEV or VulnCheck KEV, has no public exploit or PoC in any indexed source, carries no CISA Vulnrichment finding of a demonstrated exploit, and is not part of an Oracle Critical Patch Update. None of the signals that would put it in front of an engineer is present, and the volume of CVEs below that bar is too great to take one at a time, so no rule is written for it. This is a decision about what we act on, not a finding that the CVE is harmless — a patch may well be derivable, and a low-severity defect can still be one link in a longer chain.
Candidate fix	https://github.com/altcha-org/altcha-lib-ex/commit/09b2bad466ad0338a5b24245380950ea9918333e : a commit: the change itself

Decided by

Medium or Low severity, no CISA or VulnCheck KEV listing, no PoC clearing the evidence bar, no CISA verdict, no Oracle advisory

Finding

This CVE is MEDIUM severity, is not listed in CISA KEV or VulnCheck KEV, has no public exploit or PoC in any indexed source, carries no CISA Vulnrichment finding of a demonstrated exploit, and is not part of an Oracle Critical Patch Update. None of the signals that would put it in front of an engineer is present, and the volume of CVEs below that bar is too great to take one at a time, so no rule is written for it. This is a decision about what we act on, not a finding that the CVE is harmless — a patch may well be derivable, and a low-severity defect can still be one link in a longer chain.

Candidate fix

https://github.com/altcha-org/altcha-lib-ex/commit/09b2bad466ad0338a5b24245380950ea9918333e : a commit: the change itself

Affected software and releases

Maven packages

Affected and fixed versions, from OSV.dev

Package Introduced Fixed Last affected

org.altcha:altcha 0 1.3.0 unbounded

Package	Introduced	Fixed	Last affected
`org.altcha:altcha`	0	`1.3.0`	unbounded

Products and versions

1 product, 1 version entry

Source	Vendor	Product	Scheme	Affected versions
osv	org.altcha	altcha	generic	＜ 1.3.0

Source

Vendor

Product

Scheme

Affected versions

osv

org.altcha

altcha

generic

＜ 1.3.0

References

URL	Tags
https://github.com/altcha-org/altcha-lib-ex/commit/09b2bad466ad0338a5b24245380950ea9918333e	commit
https://github.com/altcha-org/altcha-lib/security/advisories/GHSA-6gvq-jcmp-8959	WEB
https://github.com/altcha-org/altcha-lib-go/commit/4a5610745ef79895a67bac858b2e4f291c2614b8	WEB
https://github.com/altcha-org/altcha-lib-java/commit/69277651fdd6418ae10bf3a088901506f9c62114	WEB
https://github.com/altcha-org/altcha-lib-php/commit/9e9e70c864a9db960d071c77c778be0c9ff1a4d0	WEB
https://github.com/altcha-org/altcha-lib-rb/commit/4fd7b64cbbfc713f3ca4e066c2dd466e3b8d359b	WEB
https://github.com/altcha-org/altcha-lib/commit/cb95d83a8d08e273b6be15e48988e7eaf60d5c08	WEB
https://github.com/altcha-org/altcha-lib	PACKAGE
https://github.com/altcha-org/altcha-lib-java/releases/tag/v1.3.0	WEB
https://github.com/altcha-org/altcha-lib-php/releases/tag/v1.3.1	WEB

URL

Timeline

Published	2025-12-16	By the CVE Program.
NVD record modified	2026-10-07	NVD's own last-modified date for this record.

Published

2025-12-16

By the CVE Program.

NVD record modified

2026-10-07

NVD's own last-modified date for this record.

How VRT decided (17 of 24 rules ran)

17 of 24 rules ran. The rest didn't run because an earlier rule had already settled the CVE.

# Rule Outcome Status Detail

identity: Does this identifier describe a vulnerability at all? the first rule that matches decides

1 rejected no match CVE Program withdrawal of this identifier

scope: Is it a vulnerability Waratek protects? the first rule that matches decides

2 armr-patch-file no match An ARMR patch file on disk for this CVE

3 armr-secure-rule-file no match An ARMR security-rule template on disk for this CVE

4 manual-classification no match A researcher's recorded decision for this specific CVE

5 manual classification no match Manual classification of this CVE in the legacy dataset

6 non-java-upstream no match A root cause in non-Java code: an OS kernel, a C library, or a bundled runtime

7 oracle-component no match The defect being in a component of a tracked product the agent does not reach: JavaFX, the Java SE installer, the JInitiator browser plug-in, the native WebLogic proxy plug-in, or a native part of Oracle Application Server or Collaboration Suite (HTTP Server, Web Cache, Internet Directory, mail and calendar servers). Oracle gives these no CPE of their own and names them only in the description.

8 java-client-side no match Oracle's own risk-matrix note saying the CVE is reached only through untrusted code in the Java sandbox (applets, Web Start) or only through a client installation of Java, so a server running its own trusted code is not exposed

9 osv-maven matched In scope Maven packages: org.altcha:altcha

10 cna-maven-package not reached An affected Maven artifact named by the CNA itself

11 known-cpe-product not reached An NVD CPE naming a product ARMR tracks

12 cna-cpe-product not reached A CPE the CNA published naming a tracked product. Oracle publishes these on advisory day, months before NVD.

13 oracle-advisory-family not reached A tracked product family named in Oracle's own risk matrix. CPE cannot carry a suite name, only a module.

14 cna-named-product not reached A tracked product named in words by the CVE's own CNA, on a record with no CPE yet. Apache and Eclipse publish these on advisory day, before NVD adds CPE data.

15 non-deployable-product not reached The only affected product being a sealed appliance image, where Java runs but no -javaagent can be attached

16 unmatched-product not reached No tracked product matched above, and none present at all

disposition: What do we do about one that is? every rule runs

17 patch-hint matched Mitigation candidate References include candidate fix URL (commit tier): https://github.com/altcha-org/altcha-lib-ex/commit/09b2bad466ad0338a5b24245380950ea9918333e

18 open-source-maven skipped The affected package being open source on Maven, so the fix can be read

19 poc-derivable skipped An indexed exploit clearing the evidence bar to reverse-engineer, where there is no source to read

20 no-exploit skipped Nothing to build a rule from yet: no published exploit, no CISA record of exploitation and no source-level change to read

21 secure-rule-match no match A vulnerability class already blocked by an ARMR security rule

22 exploited-no-fix-or-poc skipped Somebody exploiting this CVE (a CISA or VulnCheck KEV listing, or a CISA verdict of active exploitation), with no fix, source code or PoC to build a rule from

23 below-action-threshold decided it matched No exploit published MEDIUM severity, no CISA or VulnCheck KEV listing, no public PoC clearing the evidence bar, no CISA exploitation finding, and not in an Oracle advisory — none of the signals we act on is present.

24 no-exploit-published skipped Exploit code for this candidate, published in a reviewed catalogue or a GitHub repository with 5 or more stars, or in use per CISA or VulnCheck; not only a CISA verdict, a forecast, or nothing at all

NVD ↗ · CVE.org ↗