EUVD-2026-54725
GHSA-v6w3-qrh8-qccc
Severity by source
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber
AV:N reflects remotely-triggered entropy calls; AC:L because hypervisor non-forwarding makes failure deterministic on every call; pure availability loss with no C/I impact.
Primary rating from Vendor (bcorg).
CVSS VectorVendor: bcorg
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:Amber
Lifecycle Timeline
3DescriptionCVE.org
In Bouncy Castle for Java FIPS (BC-FJA) before bc-fips 2.1.3, the native entropy source used on Intel platforms retried the CPU entropy instructions without any bound. RDSEED and RDRAND report failure through their carry flag, and the JNI seeding routine spun re-issuing the instruction for as long as that flag stayed clear, so a persistent failure of the on-chip entropy source - whether from a hardware fault, from the underlying DRBG being exhausted by contention across many cores, or from a hypervisor that does not provide the instruction - left the calling thread looping indefinitely inside the JNI call, where it could be neither interrupted nor timed out. Any operation drawing from the native entropy source could therefore hang, denying service to the application. The retry loops are now bounded (200 attempts for RDSEED and 20 for RDRAND, twice the baselines given in Intel's Digital Random Number Generator software implementation guide), pausing between attempts and, on exhaustion, clearing any partially written buffer and throwing rather than continuing to spin. The clear is performed by an un-elidable memzero, which uses a volatile pointer and an assembly memory barrier so that a compiler cannot optimise the erase away as a dead store. Bouncy Castle for Java (bcprov) is not affected, as it has no native entropy source; the 1.0.X and 2.0.X FIPS series are not affected.
Articles & Coverage 1
AnalysisAI
Unbounded retry loops in BC-FJA's JNI native entropy layer cause calling threads to hang indefinitely when Intel RDSEED or RDRAND instructions persistently fail, producing a non-interruptible thread-level denial of service in any Java FIPS application backed by bc-fips 2.1.x before 2.1.3. The affected JNI seeding routine re-issues the CPU entropy instruction without any iteration limit whenever the carry flag signals failure - a condition reproducible by hardware entropy source faults, DRBG exhaustion under heavy multi-core contention, or hypervisors that do not forward these Intel instructions to guest VMs. …
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Attack ChainAIDerived
Hypothetical attack flow derived from CVE metadata
Vulnerability AssessmentAI
| Exploitation | The vulnerability requires all of the following to be simultaneously true: the application must use bc-fips in the 2.1.x series strictly before version 2.1.3 (bc-fips 1.0.x, bc-fips 2.0.x, and the standard bcprov library are explicitly NOT affected); execution must occur on an Intel x86 platform where the JNI native entropy path is active; and one of three persistent entropy failure conditions must be present - a hardware fault in the on-chip entropy source, extreme DRBG exhaustion from simultaneous entropy requests across many CPU cores, or a hypervisor or VMM that does not forward RDRAND and RDSEED instructions to the guest. … Additional conditions and limiting factors are described in the full assessment. |
| Risk Assessment | The vendor-supplied CVSS 4.0 score of 8.7 with vector AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N reflects pure availability impact assessed at low attack complexity, which is defensible in the worst-case hypervisor scenario: if the VMM never forwards RDRAND/RDSEED to the guest, entropy failure is immediate and deterministic on every call, requiring zero attacker sophistication. … Full risk analysis with EPSS, KEV, and SSVC signal comparison available after sign-in. |
| Exploit Scenario | In a cloud environment where the hypervisor does not forward RDRAND/RDSEED to the guest VM, any inbound request to a bc-fips 2.1.x application that triggers a cryptographic operation requiring entropy seeding - such as a TLS handshake initiation, server-side key generation, or session token creation - causes the handling thread to spin permanently inside the JNI call with no recovery possible from the Java side. No exploit code, credentials, or privileged network position are required; a remote unauthenticated attacker need only send enough such requests to exhaust the application's thread pool, taking the service offline within seconds depending on pool size. |
| Remediation | Upgrade to bc-fips 2.1.3 or later, which introduces bounded retry counts (200 for RDSEED, 20 for RDRAND), inter-attempt pauses, and exception throwing on exhaustion, eliminating the infinite spin. … Detailed patch versions, workarounds, and compensating controls in full report. |
Recommended ActionAI
Within 24 hours, identify all Java applications using bc-fips versions 2.1.0 through 2.1.2 and assess which run in cloud or virtualized environments. …
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External POC / Exploit Code
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