CVE-2026-54876 (GCVE-0-2026-54876)

Vulnerability from cvelistv5 – Published: 2026-08-05 13:59 – Updated: 2026-08-05 19:31
VLAI
Title
Client-Side Memory Leak in OCSP Response Checking
Summary
Issue summary: A malicious TLS server can cause a memory leak in a TLS client that has enabled OCSP response checking by sending an OCSP response that contains no single response entries. Impact summary: An attacker can leak an attacker-tunable amount of memory per TLS handshake in a victim client application. A long-running client that repeatedly connects to a malicious server can have its memory exhausted, resulting in a Denial of Service. CWE: CWE-401: Missing Release of Memory after Effective Lifetime Description: The affected function is called during X.509 certificate chain verification when OCSP response checking is enabled with the X509_V_FLAG_OCSP_RESP_CHECK or X509_V_FLAG_OCSP_RESP_CHECK_ALL verification flags, for example when a TLS client verifies an OCSP response stapled into the TLS handshake by the server. When the received BasicOCSPResponse contains an empty SEQUENCE OF SingleResponse, which is permitted on the wire and accepted by the OpenSSL decoder, the OCSP_BASICRESP structure allocated by OCSP_response_get1_basic() was not freed because an early return bypassed the cleanup code at the end of the function. The amount of memory leaked per handshake can be amplified by the attacker by padding the certs field of the BasicOCSPResponse with bogus certificates, which are parsed and stored in the leaked structure before the empty response check triggers the early return. A long-running TLS client that repeatedly connects to a malicious server can have its memory exhausted over time. OCSP response checking is not enabled by default. Only client applications that explicitly enable the OCSP response check verification flags are affected. FIPS impact: no The FIPS modules in 4.0 and 3.6 are not affected by this issue as the affected code is outside the OpenSSL FIPS module boundary.
Severity
7.5 (High)
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
SSVC
Exploitation: none Automatable: yes Technical Impact: partial
CISA Coordinator · CISA-ADP (v2.0.3)
Decision recorded 2026-08-05 19:31 UTC
CWE
  • CWE-401 - Missing Release of Memory after Effective Lifetime
Assigner
References
Impacted products
Vendor Product Version CPE status
OpenSSL OpenSSL Affected: 4.0.0 , < 4.0.2 (semver)
Affected: 3.6.0 , < 3.6.4 (semver)
guessed Create a notification for this product.
Date Public
2026-08-05 11:43
Credits
Bhabani Sankar Das Zhenzhe Shao Mounir Idrassi
Show details on NVD website
To clipboard 

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Only client\\napplications that explicitly enable the OCSP response check\\nverification flags are affected.\\n\\nFIPS impact: no\\n\\nThe FIPS modules in 4.0 and 3.6 are not affected by this issue as the\\naffected code is outside the OpenSSL FIPS module boundary.\", \"supportingMedia\": [{\"type\": \"text/html\", \"value\": \"Issue summary: A malicious TLS server can cause a memory leak in a TLS\u003cbr\u003eclient that has enabled OCSP response checking by sending an OCSP\u003cbr\u003eresponse that contains no single response entries.\u003cbr\u003e\u003cbr\u003eImpact summary: An attacker can leak an attacker-tunable amount of memory\u003cbr\u003eper TLS handshake in a victim client application. A long-running client\u003cbr\u003ethat repeatedly connects to a malicious server can have its memory\u003cbr\u003eexhausted, resulting in a Denial of Service.\u003cbr\u003e\u003cbr\u003eCWE: CWE-401: Missing Release of Memory after Effective Lifetime\u003cbr\u003e\u003cbr\u003eDescription: The affected function is called during X.509 certificate\u003cbr\u003echain verification when OCSP response checking is enabled\u003cbr\u003ewith the X509_V_FLAG_OCSP_RESP_CHECK or X509_V_FLAG_OCSP_RESP_CHECK_ALL\u003cbr\u003everification flags, for example when a TLS client verifies an OCSP\u003cbr\u003eresponse stapled into the TLS handshake by the server.\u003cbr\u003e\u003cbr\u003eWhen the received BasicOCSPResponse contains an empty SEQUENCE OF\u003cbr\u003eSingleResponse, which is permitted on the wire and accepted by the\u003cbr\u003eOpenSSL decoder, the OCSP_BASICRESP structure allocated by\u003cbr\u003eOCSP_response_get1_basic() was not freed because an early return\u003cbr\u003ebypassed the cleanup code at the end of the function.\u003cbr\u003e\u003cbr\u003eThe amount of memory leaked per handshake can be amplified by the\u003cbr\u003eattacker by padding the certs field of the BasicOCSPResponse with\u003cbr\u003ebogus certificates, which are parsed and stored in the leaked\u003cbr\u003estructure before the empty response check triggers the early return.\u003cbr\u003eA long-running TLS client that repeatedly connects to a malicious\u003cbr\u003eserver can have its memory exhausted over time.\u003cbr\u003e\u003cbr\u003eOCSP response checking is not enabled by default. Only client\u003cbr\u003eapplications that explicitly enable the OCSP response check\u003cbr\u003everification flags are affected.\u003cbr\u003e\u003cbr\u003eFIPS impact: no\u003cbr\u003e\u003cbr\u003eThe FIPS modules in 4.0 and 3.6 are not affected by this issue as the\u003cbr\u003eaffected code is outside the OpenSSL FIPS module boundary.\", \"base64\": false}]}], \"problemTypes\": [{\"descriptions\": [{\"lang\": \"en\", \"type\": \"CWE\", \"cweId\": \"CWE-401\", \"description\": \"CWE-401 Missing Release of Memory after Effective Lifetime\"}]}], \"providerMetadata\": {\"orgId\": \"3a12439a-ef3a-4c79-92e6-6081a721f1e5\", \"shortName\": \"openssl\", \"dateUpdated\": \"2026-08-05T13:59:36.466Z\"}}}",
      "cveMetadata": "{\"cveId\": \"CVE-2026-54876\", \"state\": \"PUBLISHED\", \"dateUpdated\": \"2026-08-05T19:31:51.591Z\", \"dateReserved\": \"2026-06-16T10:18:08.636Z\", \"assignerOrgId\": \"3a12439a-ef3a-4c79-92e6-6081a721f1e5\", \"datePublished\": \"2026-08-05T13:59:36.466Z\", \"assignerShortName\": \"openssl\"}",
      "dataType": "CVE_RECORD",
      "dataVersion": "5.2"
    }
  }
}



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Forecast uses a logistic model when the trend is rising, or an exponential decay model when the trend is falling. Fitted via linearized least squares.

Sightings

Author Source Type Date Other

Nomenclature

  • Seen: The vulnerability was mentioned, discussed, or observed by the user.
  • Confirmed: The vulnerability has been validated from an analyst's perspective.
  • Published Proof of Concept: A public proof of concept is available for this vulnerability.
  • Exploited: The vulnerability was observed as exploited by the user who reported the sighting.
  • Patched: The vulnerability was observed as successfully patched by the user who reported the sighting.
  • Not exploited: The vulnerability was not observed as exploited by the user who reported the sighting.
  • Not confirmed: The user expressed doubt about the validity of the vulnerability.
  • Not patched: The vulnerability was not observed as successfully patched by the user who reported the sighting.


Detection rules are retrieved from Rulezet.