cryptlib through 3.4.4 allows a memory-cache side-channel attack on DSA and ECDSA signatures, aka the Return Of the Hidden Number Problem o…

published 2018-06-15 8 y ago modified 2026-06-17 4 mo ago also EUVD-2018-4404

cvss: 4.9; version 3.1, NVD
cisa kev: Not listed; not in CISA's catalog
epss: 0.3%; EPSS 0.3% chance of exploitation in 30 days, percentile 27%
public exploits: 0; none known

cryptlib through 3.4.4 allows a memory-cache side-channel attack on DSA and ECDSA signatures, aka the Return Of the Hidden Number Problem or ROHNP. To discover a key, the attacker needs access to either the local machine or a different virtual machine on the same physical host. NOTE: the vendor does not include side-channel attacks within its threat model

Exploit prediction

0.34% chance of exploitation in the next 30 days, higher than 27% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

nccgroup.trust https://www.nccgroup.trust/us/our-research/technical-advisory-return-of-the-hidden-number-problem/ referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by	version	score	vector
NVD	3.1	4.9	CVSS:3.1/AV:P/AC:H/PR:N/UI:N/S:C/C:H/I:N/A:N
NVD	2.0	1.9	AV:L/AC:M/Au:N/C:P/I:N/A:N

Classification

Weakness

CWE-200 Exposure of Sensitive Information to an Unauthorized Actor
CWE-320 Key Management Errors

References

nccgroup.trust /us/our-research/technical-advisory-return-of-the-hidden-number-problem/
exploit, technical-description, third-party-advisory

Sources

CVE List CVE-2018-12433
NVD CVE-2018-12433

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.

Summary