CVE-2020-12399
Description
A flaw was found in the DSA signature generation function in nss. During the process of generating a DSA signature, the nonce value 'k' is not padded, exposing the bit length. Combined with other techniques, this can result in the recovery of the DSA private key. The highest threat from this vulnerability is to data confidentiality.
Statement
A timing attack was found in the way NSS generated DSA signatures. A man-in-the-middle attacker could use this attack during DSA signature generation to recover the private key. This attack is only feasible when the attacker is local to the machine or in certain cross-VM scenarios where the signature is being generated. Attacks over the network or via the internet are not feasible.
Firefox and Thunderbird on Red Hat Enterprise Linux are built against the system nss library.
Mitigation
Mitigation for this issue is either not available or the currently available options do not meet the Red Hat Product Security criteria comprising ease of use and deployment, applicability to widespread installation base or stability.
Common Vulnerability Scoring System (CVSS) Score Details
Info alert:Important note
CVSS scores for open source components depend on vendor-specific factors (e.g. version or build chain). Therefore, Red Hat's score and impact rating can be different from NVD and other vendors. Red Hat remains the authoritative CVE Naming Authority (CNA) source for its products and services (see Red Hat classifications).
CVSS v3 Score Breakdown
| Red Hat | NVD | cve.org | |
|---|---|---|---|
| Base Score | 4.4 | 4.4 | N/A |
| Attack Vector | Local | Local | N/A |
| Attack Complexity | High | High | N/A |
| Privileges Required | Low | Low | N/A |
| User Interaction | Required | Required | N/A |
| Scope | Unchanged | Unchanged | N/A |
| Confidentiality | High | High | N/A |
| Integrity Impact | None | None | N/A |
| Availability Impact | None | None | N/A |
Vector
Red Hat: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:N
NVD: CVSS:3.1/AV:L/AC:H/PR:L/UI:R/S:U/C:H/I:N/A:N
Understanding the Weakness (CWE)
Confidentiality
Technical Impact: Read Application Data
The confidentiality of sensitive data may be compromised by the use of a broken or risky cryptographic algorithm.
Integrity
Technical Impact: Modify Application Data
The integrity of sensitive data may be compromised by the use of a broken or risky cryptographic algorithm.
Accountability,Non-Repudiation
Technical Impact: Hide Activities
If the cryptographic algorithm is used to ensure the identity of the source of the data (such as digital signatures), then a broken algorithm will compromise this scheme and the source of the data cannot be proven.
Acknowledgements
Upstream acknowledges Cesar Pereida Garcia (Tampere University) and Network and Information Security Group (Tampere University) as the original reporters.
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