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Fencer Intel
medium 4.9

CVE-2018-12437 json

LibTomCrypt through 1.18.1 allows a memory-cache side-channel attack on ECDSA signatures, aka the Return Of the Hidden Number Problem or RO…

published 2018-06-15 8 y ago modified 2026-06-17 4 mo ago also EUVD-2018-4408

cvss
4.9
version 3.1, NVD
cisa kev
Not listed
not in CISA's catalog
epss
0.5%
EPSS 0.5% chance of exploitation in 30 days, percentile 45%
public exploits
0
none known

Summary

LibTomCrypt through 1.18.1 allows a memory-cache side-channel attack on ECDSA signatures, aka the Return Of the Hidden Number Problem or ROHNP. To discover an ECDSA key, the attacker needs access to either the local machine or a different virtual machine on the same physical host.

Patch / fix

  • libtomcrypt Debian 14, Debian 13, Debian 12 1.18.2-1

debian advisories DEBIAN-CVE-2018-12437

  • libtomcrypt Ubuntu 14.04 LTS 1.17-5ubuntu0.1
  • libtomcrypt Ubuntu 16.04 LTS 1.17-7ubuntu0.1
  • libtomcrypt Ubuntu 18.04 LTS 1.18.1-1ubuntu0.1

ubuntu advisories UBUNTU-CVE-2018-12437

Ubuntu security data © Canonical Ltd., from https://github.com/canonical/ubuntu-security-notices via OSV; changed: normalised to fixed package versions per release. CC BY-SA 4.0

Vendor advisories

What the vendors themselves say about their products: affected, fixed or not affected, and what to do.

red hat product security vex CVE-2018-12437 updated cvss 5.5

libtomcrypt: memory-cache side-channel attack on ECDSA signatures

  • Red Hat CloudForms Management Engine 5 libtomcrypt Red Hat Ansible Engine 2 libtomcrypt Red Hat Enterprise Linux 7 libtomcrypt
    not affected: vulnerable code not present

Red Hat CSAF VEX © Red Hat, Inc., from https://security.access.redhat.com/data/csaf/v2/vex/; changed: reduced to product statuses and remediations. CC BY 4.0 · csaf

Exploit prediction

0.54% chance of exploitation in the next 30 days, higher than 45% of all scored CVEs (FIRST EPSS, 2026-11-09).

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

References

Sources

Fencer Intel 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.