Heap Use-After-Free in OpenSSL PKCS7verify()
Heap Use-After-Free in OpenSSL PKCS7verify() (CVE-2026-45447) Severity: High
Issue summary: A specially crafted PKCS#7 or S/MIME signed message could trigger a use-after-free during PKCS#7 signature verification.
Impact summary: A use-after-free may result in process crashes, heap corruption, or potentially remote code execution.
When processing a PKCS#7 or S/MIME signed message, if the SignedData digestAlgorithms field is present as an empty ASN.1 SET, OpenSSL may incorrectly free a caller-owned BIO during PKCS7verify(). A subsequent use of the BIO by the calling application results in a use-after-free condition.
In the common case this occurs when the application later calls BIOfree() on the BIO originally passed to PKCS7verify(). Depending on allocator behavior and application-specific BIO usage patterns, this may result in a crash or other memory corruption. In some application contexts this may potentially be exploitable for remote code execution.
Applications that process PKCS#7 or S/MIME signed messages using OpenSSL PKCS#7 APIs may be affected. Applications using the CMS APIs for this processing are not affected.
The FIPS modules in 4.0, 3.6, 3.5, 3.4, and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.
OpenSSL 4.0, 3.6, 3.5, 3.4, 3.0, 1.1.1, and 1.0.2 are vulnerable to this issue.
OpenSSL 4.0 users should upgrade to OpenSSL 4.0.1 OpenSSL 3.6 users should upgrade to OpenSSL 3.6.3. OpenSSL 3.5 users should upgrade to OpenSSL 3.5.7. OpenSSL 3.4 users should upgrade to OpenSSL 3.4.6. OpenSSL 3.0 users should upgrade to OpenSSL 3.0.21. OpenSSL 1.1.1 users should upgrade to OpenSSL 1.1.1zh (premium support customers only). OpenSSL 1.0.2 users should upgrade to OpenSSL 1.0.2zq (premium support customers only).
This issue was reported by Thai Duong (Calif.io in collaboration with Claude and Anthropic Research). on 27th April 2026. The fix was developed by Igor Ustinov.
AES-OCB IV Ignored on EVPCipher() Path
CMS AuthEnvelopedData Processing May Accept Forged Messages
Issue summary: During processing of a crafted CMS EnvelopedData message with KeyTransportRecipientInfo a NULL pointer dereference can happen.
Impact summary: Applications that process attacker-controlled CMS data may crash before authentication or cryptographic operations occur resulting in Denial of Service.
When a CMS EnvelopedData message that uses KeyTransportRecipientInfo with RSA-OAEP encryption is processed, the optional parameters field of RSA-OAEP SourceFunc algorithm identifier is examined without checking for its presence. This results in a NULL pointer dereference if the field is missing.
Applications and services that call CMSdecrypt() on untrusted input (e.g., S/MIME processing or CMS-based protocols) are vulnerable.
The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.
Issue summary: A type confusion vulnerability exists in the TimeStamp Response verification code where an ASN1TYPE union member is accessed without first validating the type, causing an invalid or NULL pointer dereference when processing a malformed TimeStamp Response file.
Impact summary: An application calling TSRESPverifyresponse() with a malformed TimeStamp Response can be caused to dereference an invalid or NULL pointer when reading, resulting in a Denial of Service.
The functions osslessgetsigningcert() and osslessgetsigningcertv2() access the signing cert attribute value without validating its type. When the type is not VASN1SEQUENCE, this results in accessing invalid memory through the ASN1TYPE union, causing a crash.
Exploiting this vulnerability requires an attacker to provide a malformed TimeStamp Response to an application that verifies timestamp responses. The TimeStamp protocol (RFC 3161) is not widely used and the impact of the exploit is just a Denial of Service. For these reasons the issue was assessed as Low severity.
The FIPS modules in 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the TimeStamp Response implementation is outside the OpenSSL FIPS module boundary.
OpenSSL 3.6, 3.5, 3.4, 3.3, 3.0 and 1.1.1 are vulnerable to this issue.
OpenSSL 1.0.2 is not affected by this issue.
Issue summary: When using the low-level OCB API directly with AES-NI or<br>other hardware-accelerated code paths, inputs whose length is not a multiple<br>of 16 bytes can leave the final partial block unencrypted and unauthenticated.<br><br>Impact summary: The trailing 1-15 bytes of a message may be exposed in<br>cleartext on encryption and are not covered by the authentication tag,<br>allowing an attacker to read or tamper with those bytes without detection.<br><br>The low-level OCB encrypt and decrypt routines in the hardware-accelerated<br>stream path process full 16-byte blocks but do not advance the input/output<br>pointers. The subsequent tail-handling code then operates on the original<br>base pointers, effectively reprocessing the beginning of the buffer while<br>leaving the actual trailing bytes unprocessed. The authentication checksum<br>also excludes the true tail bytes.<br><br>However, typical OpenSSL consumers using EVP are not affected because the<br>higher-level EVP and provider OCB implementations split inputs so that full<br>blocks and trailing partial blocks are processed in separate calls, avoiding<br>the problematic code path. Additionally, TLS does not use OCB ciphersuites.<br>The vulnerability only affects applications that call the low-level<br>CRYPTOocb128encrypt() or CRYPTOocb128decrypt() functions directly with<br>non-block-aligned lengths in a single call on hardware-accelerated builds.<br>For these reasons the issue was assessed as Low severity.<br><br>The FIPS modules in 3.6, 3.5, 3.4, 3.3, 3.2, 3.1 and 3.0 are not affected<br>by this issue, as OCB mode is not a FIPS-approved algorithm.<br><br>OpenSSL 3.6, 3.5, 3.4, 3.3, 3.0 and 1.1.1 are vulnerable to this issue.<br><br>OpenSSL 1.0.2 is not affected by this issue.
Issue summary: A type confusion vulnerability exists in the signature verification of signed PKCS#7 data where an ASN1TYPE union member is accessed without first validating the type, causing an invalid or NULL pointer dereference when processing malformed PKCS#7 data.
Impact summary: An application performing signature verification of PKCS#7 data or calling directly the PKCS7digestfromattributes() function can be caused to dereference an invalid or NULL pointer when reading, resulting in a Denial of Service.
The function PKCS7digestfromattributes() accesses the message digest attribute value without validating its type. When the type is not VASN1OCTETSTRING, this results in accessing invalid memory through the ASN1TYPE union, causing a crash.
Exploiting this vulnerability requires an attacker to provide a malformed signed PKCS#7 to an application that verifies it. The impact of the exploit is just a Denial of Service, the PKCS7 API is legacy and applications should be using the CMS API instead. For these reasons the issue was assessed as Low severity.
The FIPS modules in 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the PKCS#7 parsing implementation is outside the OpenSSL FIPS module boundary.
OpenSSL 3.6, 3.5, 3.4, 3.3, 3.0, 1.1.1 and 1.0.2 are vulnerable to this issue.
Issue summary: Calling PKCS12getfriendlyname() function on a maliciously crafted PKCS#12 file with a BMPString (UTF-16BE) friendly name containing non-ASCII BMP code point can trigger a one byte write before the allocated buffer.
Impact summary: The out-of-bounds write can cause a memory corruption which can have various consequences including a Denial of Service.
The OPENSSLuni2utf8() function performs a two-pass conversion of a PKCS#12 BMPString (UTF-16BE) to UTF-8. In the second pass, when emitting UTF-8 bytes, the helper function bmptoutf8() incorrectly forwards the remaining UTF-16 source byte count as the destination buffer capacity to UTF8putc(). For BMP code points above U+07FF, UTF-8 requires three bytes, but the forwarded capacity can be just two bytes. UTF8putc() then returns -1, and this negative value is added to the output length without validation, causing the length to become negative. The subsequent trailing NUL byte is then written at a negative offset, causing write outside of heap allocated buffer.
The vulnerability is reachable via the public PKCS12getfriendlyname() API when parsing attacker-controlled PKCS#12 files. While PKCS12parse() uses a different code path that avoids this issue, PKCS12getfriendlyname() directly invokes the vulnerable function. Exploitation requires an attacker to provide a malicious PKCS#12 file to be parsed by the application and the attacker can just trigger a one zero byte write before the allocated buffer. For that reason the issue was assessed as Low severity according to our Security Policy.
The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the PKCS#12 implementation is outside the OpenSSL FIPS module boundary.
OpenSSL 3.6, 3.5, 3.4, 3.3, 3.0 and 1.1.1 are vulnerable to this issue.
OpenSSL 1.0.2 is not affected by this issue.
Issue summary: An invalid or NULL pointer dereference can happen in an application processing a malformed PKCS#12 file.
Impact summary: An application processing a malformed PKCS#12 file can be caused to dereference an invalid or NULL pointer on memory read, resulting in a Denial of Service.
A type confusion vulnerability exists in PKCS#12 parsing code where an ASN1TYPE union member is accessed without first validating the type, causing an invalid pointer read.
The location is constrained to a 1-byte address space, meaning any attempted pointer manipulation can only target addresses between 0x00 and 0xFF. This range corresponds to the zero page, which is unmapped on most modern operating systems and will reliably result in a crash, leading only to a Denial of Service. Exploiting this issue also requires a user or application to process a maliciously crafted PKCS#12 file. It is uncommon to accept untrusted PKCS#12 files in applications as they are usually used to store private keys which are trusted by definition. For these reasons, the issue was assessed as Low severity.
The FIPS modules in 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the PKCS12 implementation is outside the OpenSSL FIPS module boundary.
OpenSSL 3.6, 3.5, 3.4, 3.3, 3.0 and 1.1.1 are vulnerable to this issue.
OpenSSL 1.0.2 is not affected by this issue.
Issue summary: Processing a malformed PKCS#12 file can trigger a NULL pointer dereference in the PKCS12itemdecryptd2iex() function.
Impact summary: A NULL pointer dereference can trigger a crash which leads to Denial of Service for an application processing PKCS#12 files.
The PKCS12itemdecryptd2iex() function does not check whether the oct parameter is NULL before dereferencing it. When called from PKCS12unpackp7encdata() with a malformed PKCS#12 file, this parameter can be NULL, causing a crash. The vulnerability is limited to Denial of Service and cannot be escalated to achieve code execution or memory disclosure.
Exploiting this issue requires an attacker to provide a malformed PKCS#12 file to an application that processes it. For that reason the issue was assessed as Low severity according to our Security Policy.
The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the PKCS#12 implementation is outside the OpenSSL FIPS module boundary.
OpenSSL 3.6, 3.5, 3.4, 3.3, 3.0, 1.1.1 and 1.0.2 are vulnerable to this issue.
Issue summary: Writing large, newline-free data into a BIO chain using the line-buffering filter where the next BIO performs short writes can trigger a heap-based out-of-bounds write.
Impact summary: This out-of-bounds write can cause memory corruption which typically results in a crash, leading to Denial of Service for an application.
The line-buffering BIO filter (BIOflinebuffer) is not used by default in TLS/SSL data paths. In OpenSSL command-line applications, it is typically only pushed onto stdout/stderr on VMS systems. Third-party applications that explicitly use this filter with a BIO chain that can short-write and that write large, newline-free data influenced by an attacker would be affected. However, the circumstances where this could happen are unlikely to be under attacker control, and BIOflinebuffer is unlikely to be handling non-curated data controlled by an attacker. For that reason the issue was assessed as Low severity.
The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the BIO implementation is outside the OpenSSL FIPS module boundary.
OpenSSL 3.6, 3.5, 3.4, 3.3, 3.0, 1.1.1 and 1.0.2 are vulnerable to this issue.
A stack buffer overflow may lead to a crash, causing Denial of Service, or potentially remote code execution.
When parsing CMS AuthEnvelopedData structures that use AEAD ciphers such as AES-GCM, the IV (Initialization Vector) encoded in the ASN.1 parameters is copied into a fixed-size stack buffer without verifying that its length fits the destination. An attacker can supply a crafted CMS message with an oversized IV, causing a stack-based out-of-bounds write before any authentication or tag verification occurs.
Applications and services that parse untrusted CMS or PKCS#7 content using AEAD ciphers (e.g., S/MIME AuthEnvelopedData with AES-GCM) are vulnerable. Because the overflow occurs prior to authentication, no valid key material is required to trigger it. While exploitability to remote code execution depends on platform and toolchain mitigations, the stack-based write primitive represents a severe risk.
The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the CMS implementation is outside the OpenSSL FIPS module boundary.
OpenSSL 3.6, 3.5, 3.4, 3.3 and 3.0 are vulnerable to this issue.
OpenSSL 1.1.1 and 1.0.2 are not affected by this issue.
OpenSSL 3.6 users should upgrade to OpenSSL 3.6.1.
OpenSSL 3.5 users should upgrade to OpenSSL 3.5.5.
OpenSSL 3.4 users should upgrade to OpenSSL 3.4.4.
OpenSSL 3.3 users should upgrade to OpenSSL 3.3.6.
OpenSSL 3.0 users should upgrade to OpenSSL 3.0.19.
Abnormal termination of an application can a cause a denial of service.
Applications performing certificate name checks (e.g., TLS clients checking server certificates) may attempt to read an invalid memory address when comparing the expected name with an otherName subject alternative name of an X.509 certificate. This may result in an exception that terminates the application program.
Note that basic certificate chain validation (signatures, dates, ...) is not affected, the denial of service can occur only when the application also specifies an expected DNS name, Email address or IP address.
TLS servers rarely solicit client certificates, and even when they do, they generally don't perform a name check against a "reference identifier" (expected identity), but rather extract the presented identity after checking the certificate chain. So TLS servers are generally not affected and the severity of the issue is Moderate.
The FIPS modules in 3.3, 3.2, 3.1 and 3.0 are not affected by this issue. OpenSSL 1.1.1 and 1.0.2 are also not affected by this issue.
OpenSSL 3.3, 3.2, 3.1 and 3.0 are vulnerable to this issue.
OpenSSL 3.3 users should upgrade to OpenSSL 3.3.2
OpenSSL 3.2 users should upgrade to OpenSSL 3.2.3
OpenSSL 3.1 users should upgrade to OpenSSL 3.1.7
OpenSSL 3.0 users should upgrade to OpenSSL 3.0.15
Incorrect Failure Handling in RSA KEM RSASVE Encapsulation
Heap Buffer Over-read in ASN.1 Content Parsing
Issue summary: An attacker-controlled CMP (Certificate Management Protocol) server could trigger a NULL pointer dereference in a CMP client application.
Issue summary: A signed integer overflow when sizing the destination buffer for Unicode output in ASN1mbstringncopy() can lead to a heap buffer overflow.
Incorrect Tag Processing for Empty Messages in AES-GCM-SIV and AES-SIV modes
FFC-DH Peer Validation Uses Attacker-Supplied q
Issue summary: When CMS password-based decryption (RFC 3211 / PWRI key unwrap) processes attacker-supplied CMS data, an attacker-chosen stream-mode KEK cipher can trigger a heap out-of-bounds read in kekunwrapkey().
Issue summary: A specially crafted password-encrypted CMS message can trigger a NULL pointer dereference during CMS decryption.
Issue summary: During processing of a crafted CMS EnvelopedData message with KeyAgreeRecipientInfo a NULL pointer dereference can happen.
Impact summary: Applications that process attacker-controlled CMS data may crash before authentication or cryptographic operations occur resulting in Denial of Service.
When a CMS EnvelopedData message that uses KeyAgreeRecipientInfo is processed, the optional parameters field of KeyEncryptionAlgorithmIdentifier is examined without checking for its presence. This results in a NULL pointer dereference if the field is missing.
Applications and services that call CMSdecrypt() on untrusted input (e.g., S/MIME processing or CMS-based protocols) are vulnerable.
The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.
Issue summary: An uncommon configuration of clients performing DANE TLSA-based server authentication, when paired with uncommon server DANE TLSA records, may result in a use-after-free and/or double-free on the client side.
Impact summary: A use after free can have a range of potential consequences such as the corruption of valid data, crashes or execution of arbitrary code.
However, the issue only affects clients that make use of TLSA records with both the PKIX-TA(0/PKIX-EE(1) certificate usages and the DANE-TA(2) certificate usage.
By far the most common deployment of DANE is in SMTP MTAs for which RFC7672 recommends that clients treat as 'unusable' any TLSA records that have the PKIX certificate usages. These SMTP (or other similar) clients are not vulnerable to this issue. Conversely, any clients that support only the PKIX usages, and ignore the DANE-TA(2) usage are also not vulnerable.
The client would also need to be communicating with a server that publishes a TLSA RRset with both types of TLSA records.
No FIPS modules are affected by this issue, the problem code is outside the FIPS module boundary.
Issue summary: When a delta CRL that contains a Delta CRL Indicator extension is processed a NULL pointer dereference might happen if the required CRL Number extension is missing.
Impact summary: A NULL pointer dereference can trigger a crash which leads to a Denial of Service for an application.
When CRL processing and delta CRL processing is enabled during X.509 certificate verification, the delta CRL processing does not check whether the CRL Number extension is NULL before dereferencing it. When a malformed delta CRL file is being processed, this parameter can be NULL, causing a NULL pointer dereference.
Exploiting this issue requires the X509VFLAGUSEDELTAS flag to be enabled in the verification context, the certificate being verified to contain a freshestCRL extension or the base CRL to have the EXFLAGFRESHEST flag set, and an attacker to provide a malformed CRL to an application that processes it.
The vulnerability is limited to Denial of Service and cannot be escalated to achieve code execution or memory disclosure. For that reason the issue was assessed as Low severity according to our Security Policy.
The FIPS modules in 3.6, 3.5, 3.4, 3.3 and 3.0 are not affected by this issue, as the affected code is outside the OpenSSL FIPS module boundary.
AES OCB fails to encrypt some bytes
A flaw was found in OpenSSL. The crehash script does not properly sanitize shell meta-characters to prevent command injection. Some operating systems distribute this script in a manner where it is automatically executed. This flaw allows an attacker to execute arbitrary commands with the privileges of the script on these operating systems.
A flaw was found in OpenSSL. It is possible to trigger an infinite loop by crafting a certificate that has invalid elliptic curve parameters. Since certificate parsing happens before verification of the certificate signature, any process that parses an externally supplied certificate may be subject to a denial of service attack.
AES-SIV implementation ignores empty associated data entries
Applications that use the functions DHcheck(), DHcheckex() or EVPPKEYparamcheck() to check a DH key or DH parameters may experience long delays. Where the key or parameters that are being checked have been obtained from an untrusted source this may lead to a Denial of Service.
Also vulnerable are the OpenSSL dhparam and pkeyparam command line applications when using the "-check" option.
The OpenSSL SSL/TLS implementation is not affected by this issue.
The OpenSSL 3.0 and 3.1 FIPS providers are not affected by this issue.
OpenSSL 3.1, 3.0, 1.1.1 and 1.0.2 are vulnerable to this issue.
http://www.openwall.com/lists/oss-security/2023/07/19/4 http://www.openwall.com/lists/oss-security/2023/07/19/5 http://www.openwall.com/lists/oss-security/2023/07/19/6 https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=1fa20cf2f506113c761777127a38bce5068740eb https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=8780a896543a654e757db1b9396383f9d8095528 https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=9a0a4d3c1e7138915563c0df4fe6a3f9377b839c https://git.openssl.org/gitweb/?p=openssl.git;a=commitdiff;h=fc9867c1e03c22ebf56943be205202e576aabf23 https://www.openssl.org/news/secadv/20230719.txt
A flaw was found in OpenSSL's Online Certificate Status Protocol (OCSP) response functionality in the signer certificate verification routines. This flaw could result in a linked application falsely believing that an x.509 Digital Certificate is either "good" or "unknown" when revoked and requires that the application use a non-default configuration. This vulnerability leads to an issue with data integrity and confidentiality.