Every CVE Search/ Get API key

CVE-2023-4421

The NSS code used for checking PKCS#1 v1.5 was leaking information useful in mounting...

6.5 MediumFix available

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. This vulnerability affects NSS < 3.61.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
Low
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
None
Availability
None

Exploit likelihood

0.76%Up 0.7 points since Dec 13, 2023
90%50%10%1%

What each source reports

NVD Score used 6.5

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. This vulnerability affects NSS < 3.61.

Record
CVE-2023-4421
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Weakness
CWE-203
Updated
2026-11-02
CVE List No score

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. This vulnerability affects NSS < 3.61.

Record
CVE-2023-4421
Updated
2026-11-02
EUVDEUVD-2023-54284 No score

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. This vulnerability affects NSS < 3.61.

Record
EUVD-2023-54284
Updated
2026-11-02
GitHub AdvisoriesGHSA-3hpv-hgvq-792m 6.5

The NSS code used for checking PKCS#1 v1.5 was leaking information useful in mounting...

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. This vulnerability affects NSS < 3.61.

Record
GHSA-3hpv-hgvq-792m
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Weakness
CWE-203
Updated
2026-11-02
OSVBELL-CVE-2023-4421 6.5

CVE-2023-4421 does not affect BellSoft software

Record
BELL-CVE-2023-4421
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
OSV 6.5

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. This vulnerability affects NSS < 3.61.

Record
CVE-2023-4421
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
Show 4 moreShow less
OSVDEBIAN-CVE-2023-4421 6.5

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. This vulnerability affects NSS < 3.61.

Record
DEBIAN-CVE-2023-4421
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
OSVOESA-2026-2612 6.5

nss security update

Network Security Services (NSS) is a set of libraries designed to support cross-platform development of security-enabled client and server applications. Applications built with NSS can support SSL v2 and v3, TLS, PKCS #5, PKCS #7, PKCS #11, PKCS #12, S/MIME, X.509 v3 certificates, and other security standards.

Security Fix(es):

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. This vulnerability affects NSS < 3.61.(CVE-2023-4421)

Record
OESA-2026-2612
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
OSVUBUNTU-CVE-2023-4421 6.5

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. This vulnerability affects NSS < 3.61.

Record
UBUNTU-CVE-2023-4421
CVSS 3.1
6.5 MediumCVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:N/A:N
Updated
2026-11-02
OSVUSN-6727-1 No score

nss vulnerabilities

It was discovered that NSS incorrectly handled padding when checking PKCS#1 certificates. A remote attacker could possibly use this issue to perform Bleichenbacher-like attacks and recover private data. This issue only affected Ubuntu 20.04 LTS. (CVE-2023-4421)

It was discovered that NSS had a timing side-channel when performing RSA decryption. A remote attacker could possibly use this issue to recover private data. (CVE-2023-5388)

It was discovered that NSS had a timing side-channel when using certain NIST curves. A remote attacker could possibly use this issue to recover private data. (CVE-2023-6135)

The NSS package contained outdated CA certificates. This update refreshes the NSS package to version 3.98 which includes the latest CA certificate bundle and other security improvements.

Record
USN-6727-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
nss
Debian:12
 before 2:3.61-1
2:3.61-1
nss
Debian:13
 before 2:3.61-1
2:3.61-1
nss
Debian:14
 before 2:3.61-1
2:3.61-1
nss
Debian:10
 before 2:3.42.1-1+deb10u7, plus listed versions
2:3.42.1-12:3.42.1-1+deb10u12:3.42.1-1+deb10u22:3.42.1-1+deb10u32:3.42.1-1+deb10u42:3.42.1-1+deb10u52:3.42.1-1+deb10u6
2:3.42.1-1+deb10u7
nss
openEuler:20.03-LTS-SP4
 before 3.54.0-13.oe2003sp4
3.54.0-13.oe2003sp4
nss
Ubuntu:Pro:14.04:LTS
 All versions, plus listed versions
2:3.15.1-1ubuntu12:3.15.2-12:3.15.3-12:3.15.3.1-12:3.15.3.1-1.1
Show 37 moreShow less
2:3.15.3.1-1.1ubuntu12:3.15.4-1ubuntu32:3.15.4-1ubuntu42:3.15.4-1ubuntu52:3.15.4-1ubuntu62:3.15.4-1ubuntu72:3.15.4-1ubuntu7.12:3.17-0ubuntu0.14.04.12:3.17.1-0ubuntu0.14.04.12:3.17.1-0ubuntu0.14.04.22:3.17.4-0ubuntu0.14.04.12:3.19.2-0ubuntu0.14.04.12:3.19.2.1-0ubuntu0.14.04.12:3.19.2.1-0ubuntu0.14.04.22:3.21-0ubuntu0.14.04.12:3.21-0ubuntu0.14.04.22:3.23-0ubuntu0.14.04.12:3.26.2-0ubuntu0.14.04.32:3.28.4-0ubuntu0.14.04.12:3.28.4-0ubuntu0.14.04.22:3.28.4-0ubuntu0.14.04.32:3.28.4-0ubuntu0.14.04.42:3.28.4-0ubuntu0.14.04.52:3.28.4-0ubuntu0.14.04.5+esm12:3.28.4-0ubuntu0.14.04.5+esm22:3.28.4-0ubuntu0.14.04.5+esm32:3.28.4-0ubuntu0.14.04.5+esm42:3.28.4-0ubuntu0.14.04.5+esm52:3.28.4-0ubuntu0.14.04.5+esm62:3.28.4-0ubuntu0.14.04.5+esm72:3.28.4-0ubuntu0.14.04.5+esm82:3.28.4-0ubuntu0.14.04.5+esm92:3.28.4-0ubuntu0.14.04.5+esm102:3.28.4-0ubuntu0.14.04.5+esm112:3.28.4-0ubuntu0.14.04.5+esm122:3.28.4-0ubuntu0.14.04.5+esm132:3.28.4-0ubuntu0.14.04.5+esm14
 None known
nss
Ubuntu:Pro:16.04:LTS
 All versions, plus listed versions
2:3.19.2-1ubuntu12:3.19.2.1-0ubuntu12:3.21-1ubuntu22:3.21-1ubuntu32:3.21-1ubuntu4
Show 21 moreShow less
2:3.23-0ubuntu0.16.04.12:3.26.2-0ubuntu0.16.04.22:3.28.4-0ubuntu0.16.04.12:3.28.4-0ubuntu0.16.04.22:3.28.4-0ubuntu0.16.04.32:3.28.4-0ubuntu0.16.04.42:3.28.4-0ubuntu0.16.04.52:3.28.4-0ubuntu0.16.04.62:3.28.4-0ubuntu0.16.04.82:3.28.4-0ubuntu0.16.04.92:3.28.4-0ubuntu0.16.04.102:3.28.4-0ubuntu0.16.04.112:3.28.4-0ubuntu0.16.04.122:3.28.4-0ubuntu0.16.04.132:3.28.4-0ubuntu0.16.04.142:3.28.4-0ubuntu0.16.04.14+esm12:3.28.4-0ubuntu0.16.04.14+esm22:3.28.4-0ubuntu0.16.04.14+esm32:3.28.4-0ubuntu0.16.04.14+esm42:3.28.4-0ubuntu0.16.04.14+esm52:3.28.4-0ubuntu0.16.04.14+esm6
 None known
nss
Ubuntu:Pro:18.04:LTS
 All versions, plus listed versions
2:3.32-1ubuntu32:3.34-1ubuntu12:3.35-2ubuntu22:3.35-2ubuntu2.12:3.35-2ubuntu2.2
Show 14 moreShow less
2:3.35-2ubuntu2.32:3.35-2ubuntu2.52:3.35-2ubuntu2.62:3.35-2ubuntu2.72:3.35-2ubuntu2.82:3.35-2ubuntu2.92:3.35-2ubuntu2.112:3.35-2ubuntu2.122:3.35-2ubuntu2.132:3.35-2ubuntu2.142:3.35-2ubuntu2.152:3.35-2ubuntu2.162:3.35-2ubuntu2.16+esm12:3.35-2ubuntu2.16+esm2
 None known
nss
Ubuntu:20.04:LTS
 before 2:3.98-0ubuntu0.20.04.1, plus listed versions
2:3.45-1ubuntu22:3.47-1ubuntu12:3.47-1ubuntu22:3.48-1ubuntu12:3.49.1-1ubuntu1
Show 8 moreShow less
2:3.49.1-1ubuntu1.12:3.49.1-1ubuntu1.22:3.49.1-1ubuntu1.42:3.49.1-1ubuntu1.52:3.49.1-1ubuntu1.62:3.49.1-1ubuntu1.72:3.49.1-1ubuntu1.82:3.49.1-1ubuntu1.9
2:3.98-0ubuntu0.20.04.1
nss
Ubuntu:22.04:LTS
 before 2:3.98-0ubuntu0.22.04.1, plus listed versions
2:3.68-1ubuntu12:3.68-1ubuntu22:3.68.2-0ubuntu12:3.68.2-0ubuntu1.12:3.68.2-0ubuntu1.2
2:3.98-0ubuntu0.22.04.1

History

History
RecordedChangedSources
first indexedCVE List, EUVD, GitHub Advisories, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2023-4421 is a medium vulnerability (CVSS 6.5) in Mozilla Nss, published October 18, 2023. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.76%, the 55th percentile. Fixed in nss 2:3.61-1.

References

Show 10 moreShow less
Pages All vulnerabilities Browse Docs Sources Guide Get API key
MoveEnter Open