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.

The Linux/Unix host has one or more packages installed that are impacted by a vulnerability without a vendor supplied patch available.

  - 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. (CVE-2026-54876)

Note that Nessus relies on the presence of the package as reported by the vendor.

The version of OpenSSL installed on the remote host is prior to 3.6.4. It is, therefore, affected by multiple vulnerabilities as referenced in the 3.6.4 advisory.

  - Issue summary: OpenSSL CMP password based protection verification only checks whether the protectionAlg     parameter was not NULL and not its ASN.1 type, before treating it as a PBMParameter. A crafted message can     contain a parameter of a different type, which is then dereferenced as an invalid pointer. Impact summary:
    A remote, unauthenticated attacker can crash an application acting as a CMP server that accepts PBM-     protected messages, or a CMP client talking to a malicious or intercepted CMP server, resulting in a     Denial of Service. CWE: CWE-476: NULL Pointer Dereference Description: When verifying the password-based     MAC protection of a CMP message, OpenSSL library reads the protectionAlg algorithm parameter with     X509_ALGOR_get0(), which returns both the parameter type and its value pointer. The value is then cast to     an ASN1_STRING and treated as the expected PBMParameter after only checking that pointer is not NULL. The     parameter type returned by X509_ALGOR_get0() was never consulted. This happens during protection     verification, before any MAC is computed, so no knowledge of the PBM shared secret is required; the only     precondition is that PBM verification is reachable. On the server side this is reached from     OSSL_CMP_SRV_process_request() for any application that stands up a CMP server accepting PBM-protected     messages, and on the client side from CMP response validation against a malicious or on-path (MITM)     server. The reliable consequence is a denial of service; there is no memory disclosure, no controlled     memory write, and no path to code execution. CMP is a specialized feature that an application must     explicitly enable. FIPS impact: no As the CMP code lives outside the FIPS module boundary, no FIPS modules     are affected by this CVE. (CVE-2026-63076)

  - Issue summary: ChaCha20-Poly1305 and AES-OCB decryption with an empty ciphertext can report success     without verifying the supplied authentication tag when the operation is finalized by calling the     EVP_Cipher() function. Impact summary: Applications calling EVP_Cipher() on an empty ciphertext and     expecting the call to check the AEAD tag may accept forged messages. CWE: CWE-354 (Improper Validation of     Integrity Check Value) Description: The EVP_Cipher() API call for AEAD ciphers behaves like a one shot     encryption and decryption call. It also verifies the AEAD tag after the decryption operation. However for     AES-OCB and ChaCha20-Poly1305 ciphers it skipped the AEAD tag verification when an empty ciphertext was     passed to the function. The callers of this function might believe that a successful return indicates a     valid AEAD tag for these ciphers, even when that has not truly been validated in this case. FIPS impact:
    no The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this CVE as the affected algorithms     are not FIPS approved and thus not implemented in the FIPS module. (CVE-2026-75803)

  - Issue summary: When OpenSSL processes QUIC traffic from a peer that repeatedly sends ack-eliciting packets     while not acknowledging ACK-only responses, the QUIC stack can retain ACK-only packet metadata for the     lifetime of the connection. Impact summary: A remote peer that can complete a QUIC handshake can cause     connection-scoped memory growth which may lead to Denial of Service through memory exhaustion, especially     with sustained traffic or many concurrent QUIC connections. CWE: CWE-770: Allocation of Resources Without     Limits or Throttling Description: When the OpenSSL QUIC stack sends an ACK-only packet, there is no     requirement by the QUIC protocol that the peer will acknowledge that ACK-only packet (i.e. it is itself     not ack-eliciting). However, the OpenSSL implementation stores the metadata about the ACK frames     regardless. In and of itself that's ok, but if a malicious peer establishes a connection, and then drives     the connection such that ACK-only packets are forced from the OpenSSL implementation peer (i.e., by     sending numerous PING frames), and then withholding any subsequent acks for ack-eliciting data, like     legitimate data, said malicious peer can force inappropriate memory growth on the OpenSSL peer,     potentially leading to a Denial of Service. The fix is to ensure that we account for the transmission of     the ACK-only packet in the packet histories high and low watermark without actually storing the ACK-only     packet metadata itself. FIPS impact: no The OpenSSL FIPS module is not affected as the QUIC code is     outside the FIPS module boundary. (CVE-2026-63075)

  - Issue summary: The OpenSSL Certificate Management Protocol (CMP) caches additional certificates     (extraCerts) sent in a CMP message, but never expunges them (for instance if they are invalid). If a     server reuses an OSSL_CMP_CTX frequently, this cache of extraCerts may grow unboundedly, and a malicious     client may flood a CMP server with requests driving this growth. Impact summary: Users utilizing a CMP     server that reuses a single OSSL_CMP_CTX for the lifetime of a server process may observe unbounded memory     growth in the event a malicious client repeatedly sends requests containing unique extra certificates,     which may lead to OOM conditions. CWE: CWE-770: Allocation of Resources Without Limits or Throttling     Description: If a remote user sends CMP messages to a server with a list of extraCerts and the message is     rejected, the extraCerts from the message remains in the server contexts untrusted certificate stack. This     exposes servers with long lived ctx objects to Denial of Service attacks in which an attacker sends     messages intending to be rejected with a large list of additional certificates repeatedly, forcing the     server to store them indefinitely. The issue was fixed by removing the added extra certs if the message is     rejected, using the same method as when the context is configured to not do caching at all. FIPS impact:
    no As the CMP code lives outside the FIPS module boundary, no FIPS modules are affected by this CVE.
    (CVE-2026-63074)

  - Issue summary: OpenSSL CMP response validation passed an unexpected response sender distinguished name     directly as the format string to `ERR_raise_data()`. Impact summary: A malicious or intercepted CMP     endpoint can crash a CMP client that enforces an expected sender or uses a pinned server certificate whose     subject becomes the default expected sender. CWE: CWE-134 (Use of Externally-Controlled Format String)     Description: When validating a received CMP message, ossl_cmp_msg_check_update() converts the peer-     supplied sender distinguished name with X509_NAME_oneline() and passes it directly as the format argument     to ERR_raise_data(). Percent characters survive the conversion, so a sender DN such as CN=%s%n reaches     BIO_vsnprintf() as an attacker-controlled format string with no matching variadic arguments. This path is     only reached when the caller configures an expected sender or pins a server certificate, which is the     normal configuration for a CMP client validating server responses. Since the attacker controls the format     string but none of the variadic arguments, such specifiers as %s and %n dereference or write through     unrelated stack contents and crash the client. The reliable consequence is a denial of service, when the     response comes from a malicious or intercepted CMP endpoint. There is no controlled memory write,     arbitrary-address read, or reliable path to remote code execution. FIPS impact: no No FIPS modules are     affected by this issue, as the CMP protocol implementation is outside the OpenSSL FIPS module boundary.
    (CVE-2026-63073)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

The version of OpenSSL installed on the remote host is prior to 4.0.2. It is, therefore, affected by multiple vulnerabilities as referenced in the 4.0.2 advisory.

  - Issue summary: OpenSSL CMS decryption sizes the key-unwrap output buffer based on querying the unwrapped     key size, but the AES-WRAP-PAD unwrap primitive can write and cleanse more bytes than that query reports,     causing an 8-byte out-of-bounds heap write. Impact summary: An attacker who supplies a crafted CMS message     can trigger a deterministic 8-byte out-of-bounds heap write when the victim decrypts it with     CMS_decrypt(), corrupting the heap and typically resulting in a Denial of Service. CWE: CWE-787: Out-of-     bounds Write Description: The key-wrap OID is potentially attacker-controlled on the wire. CMS unwrapping     allows both id-aesNNN-wrap-pad and id-aesNNN-wrap ciphers. An attacker can take a legitimate message and     change a single OID byte to select the padded variant while leaving the message otherwise valid. Since the     unwrap key is derived from the recipient's private operation (ECDH key agreement or ML-KEM decapsulation),     the RFC 5649 integrity check cannot pass, and the decryption fails with integrity failure. The write is a     fixed-size (8-byte), fixed-value (zero) heap overflow immediately past the allocation, requires no special     configuration, and is reachable from the public CMS_decrypt() function. The consequence is a heap     corruption leading to a Denial of Service. The fix in the CMS code sizes the unwrap output buffer for the     worst case so a failed unwrap cannot write past the allocation. FIPS impact: no As the CMS code lives     outside the FIPS module boundary, no FIPS modules are affected by this CVE. (CVE-2026-63072)

  - Issue summary: When OpenSSL processes QUIC traffic from a peer that repeatedly sends ack-eliciting packets     while not acknowledging ACK-only responses, the QUIC stack can retain ACK-only packet metadata for the     lifetime of the connection. Impact summary: A remote peer that can complete a QUIC handshake can cause     connection-scoped memory growth which may lead to Denial of Service through memory exhaustion, especially     with sustained traffic or many concurrent QUIC connections. CWE: CWE-770: Allocation of Resources Without     Limits or Throttling Description: When the OpenSSL QUIC stack sends an ACK-only packet, there is no     requirement by the QUIC protocol that the peer will acknowledge that ACK-only packet (i.e. it is itself     not ack-eliciting). However, the OpenSSL implementation stores the metadata about the ACK frames     regardless. In and of itself that's ok, but if a malicious peer establishes a connection, and then drives     the connection such that ACK-only packets are forced from the OpenSSL implementation peer (i.e., by     sending numerous PING frames), and then withholding any subsequent acks for ack-eliciting data, like     legitimate data, said malicious peer can force inappropriate memory growth on the OpenSSL peer,     potentially leading to a Denial of Service. The fix is to ensure that we account for the transmission of     the ACK-only packet in the packet histories high and low watermark without actually storing the ACK-only     packet metadata itself. FIPS impact: no The OpenSSL FIPS module is not affected as the QUIC code is     outside the FIPS module boundary. (CVE-2026-63075)

  - Issue summary: ChaCha20-Poly1305 and AES-OCB decryption with an empty ciphertext can report success     without verifying the supplied authentication tag when the operation is finalized by calling the     EVP_Cipher() function. Impact summary: Applications calling EVP_Cipher() on an empty ciphertext and     expecting the call to check the AEAD tag may accept forged messages. CWE: CWE-354 (Improper Validation of     Integrity Check Value) Description: The EVP_Cipher() API call for AEAD ciphers behaves like a one shot     encryption and decryption call. It also verifies the AEAD tag after the decryption operation. However for     AES-OCB and ChaCha20-Poly1305 ciphers it skipped the AEAD tag verification when an empty ciphertext was     passed to the function. The callers of this function might believe that a successful return indicates a     valid AEAD tag for these ciphers, even when that has not truly been validated in this case. FIPS impact:
    no The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this CVE as the affected algorithms     are not FIPS approved and thus not implemented in the FIPS module. (CVE-2026-75803)

  - Issue summary: OpenSSL CMP password based protection verification only checks whether the protectionAlg     parameter was not NULL and not its ASN.1 type, before treating it as a PBMParameter. A crafted message can     contain a parameter of a different type, which is then dereferenced as an invalid pointer. Impact summary:
    A remote, unauthenticated attacker can crash an application acting as a CMP server that accepts PBM-     protected messages, or a CMP client talking to a malicious or intercepted CMP server, resulting in a     Denial of Service. CWE: CWE-476: NULL Pointer Dereference Description: When verifying the password-based     MAC protection of a CMP message, OpenSSL library reads the protectionAlg algorithm parameter with     X509_ALGOR_get0(), which returns both the parameter type and its value pointer. The value is then cast to     an ASN1_STRING and treated as the expected PBMParameter after only checking that pointer is not NULL. The     parameter type returned by X509_ALGOR_get0() was never consulted. This happens during protection     verification, before any MAC is computed, so no knowledge of the PBM shared secret is required; the only     precondition is that PBM verification is reachable. On the server side this is reached from     OSSL_CMP_SRV_process_request() for any application that stands up a CMP server accepting PBM-protected     messages, and on the client side from CMP response validation against a malicious or on-path (MITM)     server. The reliable consequence is a denial of service; there is no memory disclosure, no controlled     memory write, and no path to code execution. CMP is a specialized feature that an application must     explicitly enable. FIPS impact: no As the CMP code lives outside the FIPS module boundary, no FIPS modules     are affected by this CVE. (CVE-2026-63076)

  - Issue summary: The OpenSSL Certificate Management Protocol (CMP) caches additional certificates     (extraCerts) sent in a CMP message, but never expunges them (for instance if they are invalid). If a     server reuses an OSSL_CMP_CTX frequently, this cache of extraCerts may grow unboundedly, and a malicious     client may flood a CMP server with requests driving this growth. Impact summary: Users utilizing a CMP     server that reuses a single OSSL_CMP_CTX for the lifetime of a server process may observe unbounded memory     growth in the event a malicious client repeatedly sends requests containing unique extra certificates,     which may lead to OOM conditions. CWE: CWE-770: Allocation of Resources Without Limits or Throttling     Description: If a remote user sends CMP messages to a server with a list of extraCerts and the message is     rejected, the extraCerts from the message remains in the server contexts untrusted certificate stack. This     exposes servers with long lived ctx objects to Denial of Service attacks in which an attacker sends     messages intending to be rejected with a large list of additional certificates repeatedly, forcing the     server to store them indefinitely. The issue was fixed by removing the added extra certs if the message is     rejected, using the same method as when the context is configured to not do caching at all. FIPS impact:
    no As the CMP code lives outside the FIPS module boundary, no FIPS modules are affected by this CVE.
    (CVE-2026-63074)

Note that Nessus has not tested for these issues but has instead relied only on the application's self-reported version number.

ID	Name	Product	Family	Type	Severity
332785	Linux Distros Unpatched Vulnerability : CVE-2026-54876	Nessus	Misc.	Local	high
332717	OpenSSL 3.6.0 < 3.6.4 Multiple Vulnerabilities	Nessus	Web Servers	Combined	high
332232	OpenSSL 4.0.0 < 4.0.2 Multiple Vulnerabilities	Nessus	Web Servers	Combined	high

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CVE-2026-54876

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