VulnerabilityPublished 8 Dec 2025Updated 11 Dec 2025

CVE-2025-65849: altcha · Weak Cryptography

Affects altchaSource CVE Database V5

Not known to be exploited · CVSS 9.1 Critical.

Data as of 26 Oct 2026, 17:16 UTC

CVSS 3.1 base score

9.1Critical

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.2% chance of exploitation in 30 days – higher than 12% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 8 Dec 2025
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Affected software

Product	Affected	Fixed in
GitHubaltcha-org/altcha`pkg:github/altcha-org/altcha`Other threats	Affected =0.8.0	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

European organizations should immediately assess their use of Altcha Proof-of-Work obfuscation mode, especially versions 0.8.0 and later. Given the lack of patches, organizations must consider discontinuing reliance on this mechanism for security-critical functions. Alternative, well-vetted cryptographic protections or anti-bot solutions should be deployed. Implement layered security controls such as rate limiting, behavioral analytics, and CAPTCHAs to supplement or replace PoW obfuscation. Monitor network traffic for unusual access patterns that may indicate exploitation attempts. Conduct thorough audits of data protected by Altcha PoW to identify potential exposures. Engage with the supplier for updates or patches and participate in information sharing with industry groups. Where discontinuation is not immediately feasible, restrict access to systems using this technology via network segmentation and strict access controls. Finally, update incident response plans to include this vulnerability and prepare for potential exploitation scenarios.

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.”

Impact

For European organizations, the impact of CVE-2025-65849 is significant where Altcha PoW obfuscation is used to protect sensitive data or prevent automated scraping. Confidentiality is compromised as attackers can recover the nonce and decrypt obfuscated data remotely without authentication. Integrity is also at risk since attackers could manipulate or forge data protected by the PoW mechanism. Although availability is unaffected, the breach of confidentiality and integrity could lead to data leaks, intellectual property theft, or unauthorized data manipulation. Sectors such as finance, telecommunications, e-commerce, and government services that rely on Altcha PoW for anti-bot or data protection could face reputational damage, regulatory penalties under GDPR, and operational disruptions. The supplier’s disclaimer that the product is not designed for cryptographic security suggests organizations using it as a security control may have a false sense of protection, increasing risk exposure. The absence of known exploits in the wild provides a window for proactive mitigation, but the critical severity demands urgent attention.

CWE-327Use of a Broken or Risky Cryptographic Algorithm (opens in a new tab)
Class weaknessLikelihood of exploit: HighOWASP Top 10 A04:2025: Cryptographic Failures (opens in a new tab)
The product uses a broken or risky cryptographic algorithm or protocol.
Architecture and Design · Libraries or Frameworks
When there is a need to store or transmit sensitive data, use strong, up-to-date cryptographic algorithms to encrypt that data. Select a well-vetted algorithm that is currently considered to be strong by experts in the field, and use well-tested implementations.
Architecture and Design
Ensure that the design allows one cryptographic algorithm to be replaced with another in the next generation or version. Where possible, use wrappers to make the interfaces uniform. This will make it easier to upgrade to stronger algorithms.
Architecture and Design
Carefully manage and protect cryptographic keys (see CWE-320). If the keys can be guessed or stolen, then the strength of the cryptography itself is irrelevant.
OWASP Cheat Sheets
Cryptographic Storage (opens in a new tab)
Key Management (opens in a new tab)
Transport Layer Protection (opens in a new tab)
User Privacy Protection (opens in a new tab)
Password Storage (opens in a new tab)
OWASP ASVS 4.0.3
V8.3.7 (opens in a new tab)
V2.9.3 (opens in a new tab)
V6.2.2 (opens in a new tab)
Attack patterns
Encryption Brute Forcing (opens in a new tab)
Creating a Rogue Certification Authority Certificate (opens in a new tab)
Signature Spoof (opens in a new tab)
Signature Spoofing by Improper Validation (opens in a new tab)
Cryptanalysis of Cellular Encryption (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 16 Dec 2025, 04:43 UTC

WeaknessesCWE-327

Technical details

References

Community reviews

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