CVE-2021-20305
This flaw allows an attacker to force an invalid signature, causing an assertion failure or possible validation.
Does this matter?
High impact if exploited, but EPSS currently rates exploitation as unlikely (1.74%). Schedule it in the normal patch cycle and watch for a rise in EPSS or a public exploit.
Description
A flaw was found in Nettle in versions before 3.7.2, where several Nettle signature verification functions (GOST DSA, EDDSA & ECDSA) result in the Elliptic Curve Cryptography point (ECC) multiply function being called with out-of-range scalers, possibly resulting in incorrect results. This flaw allows an attacker to force an invalid signature, causing an assertion failure or possible validation. The highest threat to this vulnerability is to confidentiality, integrity, as well as system availability.
- CVSS 3.1
- 8.1 HIGHCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
- EPSS
- 1.74% probability · 78th percentile
- Public exploits
- None in Exploit-DB
- CISA KEV
- Not listed
- Weakness
- CWE-327, CWE-787
- Affected
- nettle project/nettle · fedoraproject/fedora · redhat/enterprise linux · netapp/active iq unified manager · netapp/ontap select deploy administration utility · debian/debian linux
- Source
- secalert@redhat.com
EPSS 1.7% since 26 October 2026; no change recorded yet. Points are recorded when the score first appears and whenever it moves by a percentage point or more.
References
- https://bugzilla.redhat.com/show_bug.cgi?id=1942533Issue Tracking, Patch, Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/09/msg00008.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MQKWVVMAIDAJ7YAA3VVO32BHLDOH2E63/
- https://security.gentoo.org/glsa/202105-31Third Party Advisory
- https://security.netapp.com/advisory/ntap-20211022-0002/Third Party Advisory
- https://www.debian.org/security/2021/dsa-4933Third Party Advisory
- https://bugzilla.redhat.com/show_bug.cgi?id=1942533Issue Tracking, Patch, Third Party Advisory
- https://lists.debian.org/debian-lts-announce/2021/09/msg00008.htmlMailing List, Third Party Advisory
- https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/MQKWVVMAIDAJ7YAA3VVO32BHLDOH2E63/
- https://security.gentoo.org/glsa/202105-31Third Party Advisory
- https://security.netapp.com/advisory/ntap-20211022-0002/Third Party Advisory
- https://www.debian.org/security/2021/dsa-4933Third Party Advisory
- https://cert-portal.siemens.com/productcert/html/ssa-398330.html
Source: NVD record, EPSS from FIRST.org, KEV from CISA, exploits from Exploit-DB. Refreshed daily. Download this record as JSON.