Vulnerability-Lookup

GHSA-5CFW-78WC-WVJQ

Vulnerability from github – Published: 2026-08-05 15:32 – Updated: 2026-08-05 21:31

Details

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

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{
  "affected": [],
  "aliases": [
    "CVE-2026-54876"
  ],
  "database_specific": {
    "cwe_ids": [
      "CWE-401"
    ],
    "github_reviewed": false,
    "github_reviewed_at": null,
    "nvd_published_at": "2026-08-05T15:16:53Z",
    "severity": "HIGH"
  },
  "details": "Issue summary: A malicious TLS server can cause a memory leak in a TLS\nclient that has enabled OCSP response checking by sending an OCSP\nresponse that contains no single response entries.\n\nImpact summary: An attacker can leak an attacker-tunable amount of memory\nper TLS handshake in a victim client application. A long-running client\nthat repeatedly connects to a malicious server can have its memory\nexhausted, resulting in a Denial of Service.\n\nCWE: CWE-401: Missing Release of Memory after Effective Lifetime\n\nDescription: The affected function is called during X.509 certificate\nchain verification when OCSP response checking is enabled\nwith the X509_V_FLAG_OCSP_RESP_CHECK or X509_V_FLAG_OCSP_RESP_CHECK_ALL\nverification flags, for example when a TLS client verifies an OCSP\nresponse stapled into the TLS handshake by the server.\n\nWhen the received BasicOCSPResponse contains an empty SEQUENCE OF\nSingleResponse, which is permitted on the wire and accepted by the\nOpenSSL decoder, the OCSP_BASICRESP structure allocated by\nOCSP_response_get1_basic() was not freed because an early return\nbypassed the cleanup code at the end of the function.\n\nThe amount of memory leaked per handshake can be amplified by the\nattacker by padding the certs field of the BasicOCSPResponse with\nbogus certificates, which are parsed and stored in the leaked\nstructure before the empty response check triggers the early return.\nA long-running TLS client that repeatedly connects to a malicious\nserver can have its memory exhausted over time.\n\nOCSP response checking is not enabled by default. 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.",
  "id": "GHSA-5cfw-78wc-wvjq",
  "modified": "2026-08-05T21:31:36Z",
  "published": "2026-08-05T15:32:22Z",
  "references": [
    {
      "type": "ADVISORY",
      "url": "https://nvd.nist.gov/vuln/detail/CVE-2026-54876"
    },
    {
      "type": "WEB",
      "url": "https://github.com/openssl/openssl/commit/155b5fe0f93365e6df1c56ee3606b121080c6c12"
    },
    {
      "type": "WEB",
      "url": "https://github.com/openssl/openssl/commit/d8c51048ac037a21bae0f41cad7a3920dc7f3638"
    },
    {
      "type": "WEB",
      "url": "https://openssl-library.org/news/secadv/20260805.txt"
    },
    {
      "type": "WEB",
      "url": "http://www.openwall.com/lists/oss-security/2026/08/05/8"
    }
  ],
  "schema_version": "1.4.0",
  "severity": [
    {
      "score": "CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H",
      "type": "CVSS_V3"
    }
  ]
}

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

Vulnerability from cvelistv5 – Published: 2026-08-05 13:59 – Updated: 2026-08-05 19:31

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 (v2.0.3)

CWE

CWE-401 - Missing Release of Memory after Effective Lifetime

Assigner

openssl

References

4 references

URL	Tags
https://openssl-library.org/news/secadv/20260805.txt	vendor-advisory
https://github.com/openssl/openssl/commit/d8c5104…	patch
https://github.com/openssl/openssl/commit/155b5fe…	patch
http://www.openwall.com/lists/oss-security/2026/08/05/8

Impacted products

1 product

Vendor	Product	Version
OpenSSL	OpenSSL	Affected: 4.0.0 , < 4.0.2 (semver) Affected: 3.6.0 , < 3.6.4 (semver)

Date Public

2026-08-05 11:43

Credits

Bhabani Sankar Das Zhenzhe Shao Mounir Idrassi

Show details on NVD website

JSON

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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.

The MITRE ATT&CK techniques below are AI-generated suggestions, inferred from the description of the vulnerability by the CIRCL/vulnerability-attack-technique-classification-roberta-base model, served locally by ML-Gateway. They have not been verified by an analyst and are provided for guidance only.

Action not permitted

GHSA-5CFW-78WC-WVJQ

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

Tags

Sightings

Nomenclature