CVE-2026-54876Network attack vector

TLS client memory exhaustion via unreleased OCSP response

Published Aug 5, 2026 · Updated Aug 5, 2026

Memory leak in OpenSSL 3.6.0 through 3.6.3 and 4.0.0 through 4.0.1 allows remote attackers to exhaust TLS client memory. An early return after accepting an empty BasicOCSPResponse bypasses cleanup of the OCSP_BASICRESP allocated by OCSP_response_get1_basic(), while attacker-supplied certificates enlarge the leaked structure. Only clients that explicitly enable X509_V_FLAG_OCSP_RESP_CHECK or X509_V_FLAG_OCSP_RESP_CHECK_ALL and repeatedly connect to a malicious server are exposed to service interruption through cumulative memory exhaustion.

CVSS severity7.5
High
EPSS probability0.26%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

Memory leak in OpenSSL 3.6.0 through 3.6.3 and 4.0.0 through 4.0.1 allows remote attackers to exhaust TLS client memory. An early return after accepting an empty BasicOCSPResponse bypasses cleanup of the OCSP_BASICRESP allocated by OCSP_response_get1_basic(), while attacker-supplied certificates enlarge the leaked structure. Only clients that explicitly enable X509_V_FLAG_OCSP_RESP_CHECK or X509_V_FLAG_OCSP_RESP_CHECK_ALL and repeatedly connect to a malicious server are exposed to service interruption through cumulative memory exhaustion.

The record

CVE
CVE-2026-54876
Published
Aug 5, 2026
Updated
Aug 5, 2026
Vendor
OpenSSL Project
Product
OpenSSL
Classifications
CWE-401, T1499.004
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Aug 5, 2026CVE publishedPublication date reported by the CVE source.
  2. Aug 5, 2026Record 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=3.6.0 <3.6.4
  2. Affected versionversion=4.0.0 <4.0.2

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

OpenSSL Project · OpenSSLversion=3.6.0 <3.6.4; version=4.0.0 <4.0.2

Published CVSS scores

7.5CISA-ADPCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/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-401Missing Release of Memory after Effective Lifetime
T1499.004Application or System Exploitation Flood

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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