BC-LTS bcprov CVE-2026-15997

Exploitation requires all of the following conditions to be met simultaneously: the application must be running on ARM hardware, as the flaw is in ARM-specific native C code and does not affect other architectures; the application must be using BC-LTS bcprov-lts8on versions 2.73.0 through 2.73.12.0; and the application must be explicitly accepting and restoring memoable SHA3 or SHAKE cryptographic state from a source that an attacker controls or can influence, such as user-supplied bytes, external API payloads, or deserialized input. The CVSS 4.0 vector rates complexity as High (AC:H) with specific precondition requirements (AT:P) and required active interaction (UI:A), confirming that exploitation is not trivial even when all conditions are present. Applications using BC-LTS only for conventional SHA3/SHAKE hashing without memoable state, or that restore state exclusively from internally-generated, trusted sources, are entirely unexposed. Non-ARM deployments are not vulnerable under any configuration.

The CVSS 4.0 base score of 1.7, combined with the supplemental E:U (exploitation unreported), accurately conveys that real-world risk is very narrow despite the High confidentiality impact metric. The attack vector is local (AV:L), attack complexity is high (AC:H), specific attack target preconditions apply (AT:P), and active user or operator interaction is required (UI:A) - collectively meaning exploitation demands ARM hardware, a specific BC-LTS version, and an application that explicitly exposes memoable SHA3/SHAKE state restoration to attacker-controlled input. The VC:H rating is notable for a CWE-787 write flaw, as out-of-bounds writes more typically manifest as integrity or availability impacts rather than confidentiality; this may reflect adjacent-memory read potential through a write-then-read exploitation chain, but this mechanism is not confirmed from available data and should be verified against the vendor advisory. No EPSS score was provided in the input data. No CISA KEV listing and no public exploit code exist at time of analysis. The supplemental S:P (provider urgency: Amber) indicates the vendor considers this a real but non-emergency concern, consistent with a meaningful but tightly scoped vulnerability requiring upgrade rather than immediate incident response.

An attacker who can supply a crafted memoable SHA3/SHAKE state blob to a Java application using BC-LTS on ARM - for example, through a file upload endpoint, a deserialization flow, or an API that accepts externally-provided cryptographic state - could trigger the out-of-bounds write in the native C layer. Given the high complexity and multiple required preconditions, exploitation would require application-level research to identify a viable input path that reaches the memoable state restoration logic. No public proof-of-concept code exists at time of analysis.