CVE-2026-54876

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 X509VFLAGOCSPRESPCHECK or X509VFLAGOCSPRESPCHECK_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 OCSPBASICRESP structure allocated by OCSPresponseget1basic() 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.

Database specific

{
    "cwe_ids": [
        "CWE-401"
    ],
    "cna_assigner": "openssl",
    "unresolved_ranges": [
        {
            "source": "AFFECTED_FIELD",
            "extracted_events": [
                {
                    "introduced": "4.0.0"
                },
                {
                    "fixed": "4.0.2"
                },
                {
                    "introduced": "3.6.0"
                },
                {
                    "fixed": "3.6.4"
                }
            ]
        }
    ],
    "osv_generated_from": "https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54876.json"
}

References

Affected packages

Git / github.com/openssl/openssl

Affected ranges

Type

GIT

Repo

https://github.com/openssl/openssl

Events

Introduced

Fixed

155b5fe0f93365e6df1c56ee3606b121080c6c12

Fixed

d8c51048ac037a21bae0f41cad7a3920dc7f3638

Database specific

{
    "source": "REFERENCES"
}

Affected versions

3.*

3.6-POST-CLANG-FORMAT-WEBKIT

3.6-PRE-CLANG-FORMAT-WEBKIT

4.*

4.0-POST-CLANG-FORMAT-WEBKIT

4.0-PRE-CLANG-FORMAT-WEBKIT

Other

BEFORE_engine

OpenSSL_0_9_1c

OpenSSL_0_9_2b

OpenSSL_0_9_3

OpenSSL_0_9_3a

OpenSSL_0_9_3beta2

OpenSSL_0_9_4

OpenSSL_0_9_5a

OpenSSL_0_9_5a-beta1

OpenSSL_0_9_5a-beta2

OpenSSL_0_9_5beta1

OpenSSL_0_9_5beta2

OpenSSL_0_9_6-beta3

OpenSSL_1_1_0-pre1

OpenSSL_1_1_0-pre2

OpenSSL_1_1_0-pre3

OpenSSL_1_1_0-pre4

OpenSSL_1_1_0-pre5

OpenSSL_1_1_0-pre6

OpenSSL_1_1_1

OpenSSL_1_1_1-pre1

OpenSSL_1_1_1-pre2

OpenSSL_1_1_1-pre3

OpenSSL_1_1_1-pre4

OpenSSL_1_1_1-pre5

OpenSSL_1_1_1-pre6

OpenSSL_1_1_1-pre7

OpenSSL_1_1_1-pre8

OpenSSL_1_1_1-pre9

master-post-auto-reformat

master-post-reformat

master-pre-auto-reformat

master-pre-reformat

openssl-3.*

openssl-3.0.0-alpha1

openssl-3.0.0-alpha10

openssl-3.0.0-alpha11

openssl-3.0.0-alpha12

openssl-3.0.0-alpha13

openssl-3.0.0-alpha14

openssl-3.0.0-alpha15

openssl-3.0.0-alpha16

openssl-3.0.0-alpha17

openssl-3.0.0-alpha2

openssl-3.0.0-alpha3

openssl-3.0.0-alpha4

openssl-3.0.0-alpha5

openssl-3.0.0-alpha6

openssl-3.0.0-alpha7

openssl-3.0.0-alpha8

openssl-3.0.0-alpha9

openssl-3.0.0-beta1

openssl-3.0.0-beta2

openssl-3.2.0-alpha1

openssl-3.2.0-alpha2

openssl-3.4.0-alpha1

openssl-3.6.0

openssl-3.6.0-alpha1

openssl-3.6.0-beta1

openssl-3.6.1

openssl-3.6.2

openssl-3.6.3

openssl-4.*

openssl-4.0.0

openssl-4.0.0-alpha1

openssl-4.0.0-beta1

openssl-4.0.1

Database specific

vanir_signatures

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            "length": 1750.0,
            "function_hash": "160641891841475924494476073364912984925"
        },
        "deprecated": false,
        "source": "https://github.com/openssl/openssl/commit/155b5fe0f93365e6df1c56ee3606b121080c6c12",
        "signature_type": "Function",
        "target": {
            "file": "crypto/x509/x509_vfy.c",
            "function": "check_cert_ocsp_resp"
        },
        "signature_version": "v1",
        "id": "CVE-2026-54876-25e2b498"
    },
    {
        "digest": {
            "length": 1750.0,
            "function_hash": "160641891841475924494476073364912984925"
        },
        "deprecated": false,
        "source": "https://github.com/openssl/openssl/commit/d8c51048ac037a21bae0f41cad7a3920dc7f3638",
        "signature_type": "Function",
        "target": {
            "file": "crypto/x509/x509_vfy.c",
            "function": "check_cert_ocsp_resp"
        },
        "signature_version": "v1",
        "id": "CVE-2026-54876-c3ef82e6"
    },
    {
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "303866564082954206206029976445149480800",
                "41104825234589676860157793468198067856",
                "97759028652397814767519481234710209452",
                "297295048248541998539773943654436570891",
                "223629964282213138350637630234383941186",
                "243959413222545377980179615990557206967"
            ]
        },
        "deprecated": false,
        "source": "https://github.com/openssl/openssl/commit/155b5fe0f93365e6df1c56ee3606b121080c6c12",
        "signature_type": "Line",
        "target": {
            "file": "crypto/x509/x509_vfy.c"
        },
        "signature_version": "v1",
        "id": "CVE-2026-54876-c9e31098"
    },
    {
        "digest": {
            "threshold": 0.9,
            "line_hashes": [
                "303866564082954206206029976445149480800",
                "41104825234589676860157793468198067856",
                "97759028652397814767519481234710209452",
                "297295048248541998539773943654436570891",
                "223629964282213138350637630234383941186",
                "243959413222545377980179615990557206967"
            ]
        },
        "deprecated": false,
        "source": "https://github.com/openssl/openssl/commit/d8c51048ac037a21bae0f41cad7a3920dc7f3638",
        "signature_type": "Line",
        "target": {
            "file": "crypto/x509/x509_vfy.c"
        },
        "signature_version": "v1",
        "id": "CVE-2026-54876-eae8e811"
    }
]

source

"https://storage.googleapis.com/cve-osv-conversion/osv-output/CVE-2026-54876.json"

vanir_signatures_modified

"2026-08-07T08:11:15Z"