CVE-2025-65548
Published: 08 December 2025
Summary
CVE-2025-65548 is a critical-severity Improper Validation of Specified Quantity in Input (CWE-1284) vulnerability in Cashu Nutshell. Its CVSS base score is 9.1 (Critical).
Operationally, exploitation aligns with the MITRE ATT&CK technique Application or System Exploitation (T1499.004); ranked at the 31.0th percentile by exploit likelihood (below the median); it is not currently listed in the CISA KEV catalog; a public proof-of-concept is referenced.
The strongest mitigations our analysis identified are NIST 800-53 SC-5 (Denial-of-service Protection) and SC-6 (Resource Availability).
Deeper analysis
CVE-2025-65548 is a vulnerability in the nutshell implementation (cashubtc/nuts) prior to version 0.18.0, stemming from NUT-14's support for creating Cashu tokens backed by a preimage hash. When such a token is spent, the mint stores the provided preimage without validating its size, enabling attackers to supply arbitrarily large data. This leads to denial-of-service via exhaustion of the mint's database and disk storage. The issue is rated at CVSS 9.1 (CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N) and maps to CWE-1284 (Improper Validation of Specified Quantity in Input).
The vulnerability is exploitable remotely by unauthenticated attackers (PR:N) with low complexity over the network (AV:N). An attacker can create a Cashu token with a preimage hash, then redeem it by submitting an oversized preimage, causing the mint to store excessive data and potentially crash or render the service unavailable due to storage depletion. The high confidentiality and integrity impacts per CVSS suggest potential for data exposure or corruption alongside the storage DoS.
Advisories reference public disclosures on Bitcointalk and Delving Bitcoin detailing the denial-of-service via HTLC in Cashu, along with NUT specifications in GitHub (nuts/07.md and 14.md). Mitigation involves upgrading nutshell to version 0.18.0 or later, which presumably adds preimage size validation, as the flaw affects only prior releases.
EU & UK References
- 🇪🇺 ENISA EUVD: EUVD-2025-201796
Vulnerability details
NUT-14 allows cashu tokens to be created with a preimage hash. However, nutshell (cashubtc/nuts) before 0.18.0 do not validate the size of preimage when the token is spent. The preimage is stored by the mint and attacker can exploit this…
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vulnerability to fill the mint's db nd disk with arbitrary data.
- CWE(s)
Related Threats
MITRE ATT&CK Enterprise TechniquesAI
Why these techniques?
Vulnerability enables denial of service by exploiting lack of preimage size validation to store arbitrary large data in mint's DB and disk, exhausting endpoint resources.
CVEs Like This One
Affected Assets
Mitigating Controls
Mitigating Controls (NIST 800-53 r5) AI
Directly mandates validation of information inputs including size and quantity, preventing storage of oversized preimages in the mint's database.
Provides protection against denial-of-service attacks through resource exhaustion, such as disk and database depletion from large preimages.
Ensures resource availability by protecting against exhaustion of storage resources exploited by arbitrary large preimage data.