Skip to content
Fencer Vulns
medium 5.9

CVE-2018-20187 json

A side-channel issue was discovered in Botan before 2.9.0.

published 2019-03-08 7 y ago modified 2026-06-17 4 mo ago also EUVD-2018-12754

cvss
5.9
version 3.0, NVD
cisa kev
Not listed
not in CISA's catalog
epss
1.5%
EPSS 1.5% chance of exploitation in 30 days, percentile 74%
public exploits
0
none known

Summary

A side-channel issue was discovered in Botan before 2.9.0. An attacker capable of precisely measuring the time taken for ECC key generation may be able to derive information about the high bits of the secret key, as the function to derive the public point from the secret scalar uses an unblinded Montgomery ladder whose loop iteration count depends on the bitlength of the secret. This issue affects only key generation, not ECDSA signatures or ECDH key agreement.

Patch / fix

  • botan_project botan 2.9.0
  • botan Debian 13, Debian 12 2.9.0-2

debian advisories DEBIAN-CVE-2018-20187

  • Botan openSUSE Tumbleweed 2.18.1-1.3

opensuse advisories openSUSE-SU-2024:10594-1

  • botan Alpine 3.21, Alpine 3.20, Alpine 3.19 +9 more 2.9.0-r0

alpine advisories ALPINE-CVE-2018-20187

Alpine secdb © Alpine Linux, from https://secdb.alpinelinux.org 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-2018-20187 updated cvss 2.5

botan: Side channel possible during ECC generation

  • Red Hat All currently supported Red Hat products
    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

1.52% chance of exploitation in the next 30 days, higher than 74% of all scored CVEs (FIRST EPSS, 2026-11-08).

CVSS scores

assigned by version score vector
NVD 3.0 5.9 CVSS:3.0/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N
NVD 2.0 4.3 AV:N/AC:M/Au:N/C:P/I:N/A:N

Classification

Weakness

References

Sources

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.