VulnerabilityPublished 19 Mar 2024Updated 4 Nov 2025

CVE-2023-5388: Mozilla Firefox · NSS susceptible to timing attack against RSA decryption

Affects Mozilla FirefoxSource CVE Database V5

Not known to be exploited · CVSS 6.5 Medium : upgrade to 124 when convenient.

Data as of 26 Oct 2026, 12:54 UTC

CVSS 3.1 base score

6.5Medium

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.9% chance of exploitation in 30 days – higher than 61% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 124

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: None
Availability: Low

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 19 Mar 2024
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 26 Oct 2026.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC or the CVSS exploit maturity reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Mozilla Firefox to 124.

Affected software

Product	Affected	Fixed in
Mozilla Firefox	Affected <124	Fixed in 124

AI-suggested

If you cannot patch yet, organizations should consider the following mitigations: 1) Limit exposure by restricting network access to critical systems running vulnerable software, especially from untrusted networks. 2) Employ network monitoring to detect unusual timing or traffic patterns that could indicate exploitation attempts. 3) Use alternative browsers or email clients that do not rely on the vulnerable NSS versions if immediate patching is not feasible. 4) Implement strict cryptographic key management practices, including regular key rotation and use of hardware security modules (HSMs) to reduce the impact of key exposure. 5) Educate security teams about timing attacks and side-channel risks to improve detection and response capabilities. 6) Coordinate with Mozilla security advisories and subscribe to vulnerability notifications to stay informed about patch releases and exploit developments. 7) Conduct internal audits to identify all systems running affected versions and prioritize remediation accordingly.

Description

NSS was susceptible to a timing side-channel attack when performing RSA decryption. This attack could potentially allow an attacker to recover the private data. This vulnerability affects Firefox < 124, Firefox ESR < 115.9, and Thunderbird < 115.9.

Impact

For European organizations, this vulnerability poses a risk to the confidentiality of encrypted communications, particularly those relying on Firefox or Thunderbird for secure email and web browsing. Sensitive data such as private keys, session tokens, or encrypted messages could be exposed if an attacker successfully performs the timing attack. This is especially critical for sectors like finance, government, healthcare, and critical infrastructure where data confidentiality is paramount. The vulnerability could facilitate further attacks such as man-in-the-middle or data exfiltration if private keys are compromised. Although no integrity or availability impact is expected, the breach of confidentiality alone can lead to significant regulatory and reputational damage under GDPR and other data protection laws. The remote and unauthenticated nature of the attack increases the threat surface, as attackers do not need insider access or user interaction. Organizations using outdated versions of Firefox or Thunderbird are particularly vulnerable. The absence of known exploits in the wild reduces immediate risk but does not eliminate the potential for future attacks once exploit code becomes available.

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 4 Nov 2025, 19:28 UTC

Technical details

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