CVE-2023-5388Public exploitNetwork attack vector

Private-data recovery via variable-time RSA decryption

Published Mar 19, 2024 · Updated Nov 4, 2025

NSS timing leakage in Firefox before 124, Firefox ESR before 115.9, and Thunderbird before 115.9 allows attackers to recover private data. NSS MPI clamping shortens decrypted integers with zero high-order limbs, so unblinding and byte-string conversion take input-dependent time. Repeated attacker-selected RSA ciphertexts expose a timing oracle that can decrypt one intercepted ciphertext; the attack does not reveal the private key.

CVSS severity6.5
Medium
EPSS probability0.82%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

NSS timing leakage in Firefox before 124, Firefox ESR before 115.9, and Thunderbird before 115.9 allows attackers to recover private data. NSS MPI clamping shortens decrypted integers with zero high-order limbs, so unblinding and byte-string conversion take input-dependent time. Repeated attacker-selected RSA ciphertexts expose a timing oracle that can decrypt one intercepted ciphertext; the attack does not reveal the private key.

The record

CVE
CVE-2023-5388
Published
Mar 19, 2024
Updated
Nov 4, 2025
Vendor
Mozilla
Product
Firefox
Classifications
Unavailable
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Mar 19, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 4, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <124

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <124
Mozilla · Thunderbirdversion=unspecified <115.9
Mozilla · Firefox ESRversion=unspecified <115.9

Published CVSS scores

6.5UbuntuCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:L/I:N/A:L
5.9Amazon LinuxCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:N/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

No sourced classifications are available.

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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