CVE-2023-6258Network attack vector

RSA plaintext recovery via PKCS#1 timing oracle

Published Jan 30, 2024 · Updated Jun 17, 2025

PKCS#1 v1.5 decryption in Fedora Linux's pkcs11-provider allows remote attackers to recover plaintext through timing observations. The RSA decryption path in src/asymmetric_cipher.c exposes distinguishable processing behavior for malformed PKCS#1 v1.5 ciphertexts instead of making rejection uniform. Exploitation requires repeated decryption queries against a service that uses an RSA private key through the provider, enabling plaintext recovery without direct key access.

CVSS severity8.1
High
EPSS probability0.56%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

PKCS#1 v1.5 decryption in Fedora Linux's pkcs11-provider allows remote attackers to recover plaintext through timing observations. The RSA decryption path in src/asymmetric_cipher.c exposes distinguishable processing behavior for malformed PKCS#1 v1.5 ciphertexts instead of making rejection uniform. Exploitation requires repeated decryption queries against a service that uses an RSA private key through the provider, enabling plaintext recovery without direct key access.

The record

CVE
CVE-2023-6258
Published
Jan 30, 2024
Updated
Jun 17, 2025
Vendor
Fedora Project
Product
Fedora Linux
Classifications
CWE-1300, CWE-203
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jan 30, 2024CVE publishedPublication date reported by the CVE source.
  2. Jun 17, 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?

Affected versions are unavailable in this record. Check the vendor advisory for version and patch details.

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Fedora Project · Fedora LinuxAffected versions are unavailable in this record.

Published CVSS scores

8.1Red Hat, Inc.CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H
8.1National Vulnerability DatabaseCVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:H/I:H/A:H

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 exploitUnconfirmed

Weakness, pattern, technique

CWE-1300Improper Protection of Physical Side Channels
CWE-203Observable Discrepancy

Public exploit references

No public exploit references are available in this record.

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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