CVE-2023-3817Network attack vector

Service interruption via oversized DH q validation

Published Jul 31, 2023 · Updated May 5, 2025

Denial of service in affected OpenSSL branches allows attackers to cause long delays by supplying untrusted DH parameters with an oversized q. DH_check() fails to reject q values at least as large as p before running expensive modular exponentiation, primality, and division checks. Reachability requires DH_check(), DH_check_ex(), EVP_PKEY_param_check(), dhparam -check, or pkeyparam -check to process untrusted parameters; SSL/TLS and the 3.0 and 3.1 FIPS providers are unaffected.

CVSS severity5.3
Medium
EPSS probability3.05%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Denial of service in affected OpenSSL branches allows attackers to cause long delays by supplying untrusted DH parameters with an oversized q. DH_check() fails to reject q values at least as large as p before running expensive modular exponentiation, primality, and division checks. Reachability requires DH_check(), DH_check_ex(), EVP_PKEY_param_check(), dhparam -check, or pkeyparam -check to process untrusted parameters; SSL/TLS and the 3.0 and 3.1 FIPS providers are unaffected.

The record

CVE
CVE-2023-3817
Published
Jul 31, 2023
Updated
May 5, 2025
Vendor
OpenSSL Project
Product
OpenSSL
Classifications
CWE-606, T1499
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jul 31, 2023CVE publishedPublication date reported by the CVE source.
  2. May 5, 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=1.0.2 <1.0.2zi
  2. Affected versionversion=1.1.1 <1.1.1v
  3. Affected versionversion=3.0.0 <3.0.10
  4. Affected versionversion=3.1.0 <3.1.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenSSL Project · OpenSSLversion=1.0.2 <1.0.2zi; version=1.1.1 <1.1.1v; version=3.0.0 <3.0.10; version=3.1.0 <3.1.2

Published CVSS scores

5.3CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L
5.3NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:L

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-606Unchecked Input for Loop Condition
T1499Endpoint Denial of Service

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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