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Vulnerability details: VCID-pjmh-gvqz-47et
Vulnerability ID VCID-pjmh-gvqz-47et
Aliases CVE-2023-4421
Summary The NSS code used for checking PKCS#1 v1.5 was leaking information useful in mounting Bleichenbacher-like attacks. Both the overall correctness of the padding as well as the length of the encrypted message was leaking through timing side-channel. By sending large number of attacker-selected ciphertexts, the attacker would be able to decrypt a previously intercepted PKCS#1 v1.5 ciphertext (for example, to decrypt a TLS session that used RSA key exchange), or forge a signature using the victim's key. The issue was fixed by implementing the implicit rejection algorithm, in which the NSS returns a deterministic random message in case invalid padding is detected, as proposed in the Marvin Attack paper.
Status Published
Exploitability 0.5
Weighted Severity 5.9
Risk 3.0
Affected and Fixed Packages Package Details
Weaknesses (2)
CWE-208 Observable Timing Discrepancy
CWE-203 Observable Discrepancy
System Score Found at
cvssv3 6.5 https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2023-4421.json
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
epss 0.0022 https://api.first.org/data/v1/epss?cve=CVE-2023-4421
cvssv3.1 5.9 https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
cvssv3.1 6.5 https://nvd.nist.gov/vuln/detail/CVE-2023-4421
generic_textual none https://www.mozilla.org/en-US/security/advisories/mfsa2023-53
Reference id Reference type URL
https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2023-4421.json
https://api.first.org/data/v1/epss?cve=CVE-2023-4421
https://bugzilla.mozilla.org/show_bug.cgi?id=1651411
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2023-4421
https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
https://www.mozilla.org/security/advisories/mfsa2023-53/
2238677 https://bugzilla.redhat.com/show_bug.cgi?id=2238677
cpe:2.3:a:mozilla:nss:*:*:*:*:*:*:*:* https://nvd.nist.gov/vuln/search/results?adv_search=true&isCpeNameSearch=true&query=cpe:2.3:a:mozilla:nss:*:*:*:*:*:*:*:*
CVE-2023-4421 https://nvd.nist.gov/vuln/detail/CVE-2023-4421
mfsa2023-53 https://www.mozilla.org/en-US/security/advisories/mfsa2023-53
USN-6727-1 https://usn.ubuntu.com/6727-1/
No exploits are available.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N Found at https://access.redhat.com/hydra/rest/securitydata/cve/CVE-2023-4421.json
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N Found at https://ftp.suse.com/pub/projects/security/yaml/suse-cvss-scores.yaml
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N Found at https://nvd.nist.gov/vuln/detail/CVE-2023-4421
Attack Vector (AV) Attack Complexity (AC) Privileges Required (PR) User Interaction (UI) Scope (S) Confidentiality Impact (C) Integrity Impact (I) Availability Impact (A)

network

adjacent_network

local

physical

low

high

none

low

high

none

required

unchanged

changed

high

low

none

high

low

none

high

low

none
Exploit Prediction Scoring System (EPSS)
Percentile 0.44701
EPSS Score 0.0022
Published At July 30, 2025, 12:55 p.m.
Date Actor Action Source VulnerableCode Version
2025-07-31T08:09:35.364207+00:00 Mozilla Importer Import https://github.com/mozilla/foundation-security-advisories/blob/master/announce/2023/mfsa2023-53.yml 37.0.0