Executive brief
A performance issue in the Linux kernel's random number generation system could allow a local user to cause system slowdowns or temporary freezes. By requesting random data frequently, an attacker can force the system to spend excessive time waiting for internal locks, impacting the responsiveness of other applications. This primarily affects the availability of system resources rather than the confidentiality of data.
Technical details
A vulnerability in the Linux kernel's crypto/jitterentropy-kcapi.c component arises from the use of a spinlock (jent_lock) across the jent_read_entropy() call. Because jent_read_entropy() performs time-intensive jitter collection and SHA3 conditioning, the spinlock remains held for an extended duration. In multi-core environments, parallel readers attempting to access the RNG will spin while waiting for the lock, leading to non-preemptible lock hold times and potential system stalls. The fix replaces the spinlock with a mutex, allowing contending threads to sleep rather than spin-wait. This issue is reachable by local users capable of triggering RNG requests.
Affected products
- Linux Linux Kernel 4.2 to 6.6.140, 6.12.90, 6.18.32, 7.0.9
Timeline
- 2026-03-30: patched: Initial patch authored
- 2026-06-24: disclosed: CVE published
References
- https://git.kernel.org/stable/c/01d798e9feb30212952d4e992801ba6bd6a82351
- https://git.kernel.org/stable/c/18216b8ab6904753eaf31baf453cb02ecd202ba4
- https://git.kernel.org/stable/c/4c03e6eb98443dc4d6d422a9780034a5b75376b4
- https://git.kernel.org/stable/c/ec427dc5286da1ed08f2d510e2147a7581b0cb02
- https://git.kernel.org/stable/c/ff734dbd9e2432601a6dcd167cfb0bf8a36d1880