CVE-2021-3580Network attack vector

Application crash via unchecked RSA ciphertext range

Published Aug 5, 2021 · Updated Nov 19, 2024

Improper input validation in GNU Project Nettle before 3.7.3 allows remote attackers to crash applications through malformed RSA ciphertext. The rsa_decrypt, rsa_decrypt_tr, and rsa_sec_decrypt routines accept zero or out-of-range ciphertext instead of rejecting values outside 0 < ciphertext < n. Exposure requires an application that passes attacker-controlled RSA ciphertext to these routines; a crash interrupts that application's service.

CVSS severity7.5
High
EPSS probability2.71%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Improper input validation in GNU Project Nettle before 3.7.3 allows remote attackers to crash applications through malformed RSA ciphertext. The rsa_decrypt, rsa_decrypt_tr, and rsa_sec_decrypt routines accept zero or out-of-range ciphertext instead of rejecting values outside 0 < ciphertext < n. Exposure requires an application that passes attacker-controlled RSA ciphertext to these routines; a crash interrupts that application's service.

The record

CVE
CVE-2021-3580
Published
Aug 5, 2021
Updated
Nov 19, 2024
Vendor
GNU Project
Product
Nettle
Classifications
CWE-20, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 5, 2021CVE publishedPublication date reported by the CVE source.
  2. Nov 19, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

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  1. Affected versionversion=nettle 3.7.3

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

GNU Project · Nettleversion=nettle 3.7.3

Published CVSS scores

7.5NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
5.0NIST NVDAV:N/AC:L/Au:N/C:N/I:N/A:P

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.

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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-20Improper Input Validation
T1499.004Endpoint Denial of Service: Application or System Exploitation

Public exploit references

No public exploit references are available in this record.

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Technologies

Your stack

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Your stack

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