Openssl: >> Openssl >> 1.1.1b Security Vulnerabilities
Issue summary: Receiving a DTLS record for a future epoch while a handshake
is in progress causes OpenSSL to buffer far more memory than the record
itself requires.
Impact summary: A peer can use a small amount of network traffic to make an
OpenSSL DTLS endpoint retain a disproportionately large amount of memory,
which may lead to a Denial of Service.
CWE: CWE-405: Asymmetric Resource Consumption (Amplification)
Description: While a DTLS handshake is in progress, a peer may legitimately
have already moved on to the next epoch (for example, having sent its
ChangeCipherSpec and Finished messages) before the local endpoint has
processed the same transition, typically because of reordering on the
underlying UDP transport. OpenSSL buffers such early records so that they
can be processed once the local endpoint catches up.
Buffering a record currently retains the entire read buffer it arrived in,
which is sized to hold the largest possible DTLS record (around 16
kilobytes), rather than just the bytes that make up the record itself. Up
to 100 such records may be buffered per connection. As a result, a peer
that sends a stream of small forged records claiming to belong to the next
epoch can cause an OpenSSL DTLS endpoint to retain around 1.7 megabytes of
memory, despite sending only a small fraction of that amount of data over
the network.
An attacker therefore gains a memory amplification factor of around 1200,
and can multiply the effect across as many associations as it is able to
open, making this a remote memory exhaustion Denial of Service risk for
DTLS servers. Since the memory retained per connection remains bounded,
and any limit an application already places on the number of concurrent
associations also bounds the total exposure, this issue has been assessed
as Low severity.
FIPS impact: no
No FIPS modules are 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 4.0.2.
OpenSSL 3.6 users should upgrade to OpenSSL 3.6.4.
OpenSSL 3.5 users should upgrade to OpenSSL 3.5.8.
OpenSSL 3.4 users should upgrade to OpenSSL 3.4.7.
OpenSSL 3.0 users should upgrade to OpenSSL 3.0.22.
Premium support customers only:
OpenSSL 1.1.1 users should upgrade to OpenSSL 1.1.1zi
OpenSSL 1.0.2 users should upgrade to OpenSSL 1.0.2zr
This issue was reported on 18 May 2026 by Amazon Web Services.
The fix has been developed by Matt Caswell.
-- cut (non-publishing metadata for internal use) --
Reported by: Amazon Web Services
Fixed by: Matt Caswell
CVSS Score
7.5
EPSS Score
0.005
Published
2026-08-25
Issue summary: A signed integer overflow when sizing the destination
buffer for Unicode output in ASN1_mbstring_ncopy() can lead to a heap
buffer overflow.
Impact summary: A heap buffer overflow may lead to a crash or possibly
attacker controlled code execution or other undefined behaviour.
In ASN1_mbstring_copy() and ASN1_mbstring_ncopy() the destination
size for Unicode output is computed in a signed int: by left shift
of the input character count for BMPSTRING (UTF-16) and
UNIVERSALSTRING (UTF-32), and by summing per-character byte counts
for UTF8STRING. The calculation overflows when the input reaches
around 2^30 characters. In the worst case (UNIVERSALSTRING at 2^30
characters) the size wraps to zero, OPENSSL_malloc(1) is called, and
the subsequent character copy writes several gigabytes past the
one-byte allocation.
X.509 certificate processing routes through ASN1_STRING_set_by_NID(),
whose DIRSTRING_TYPE mask excludes UNIVERSALSTRING and whose per-NID
size limits cap the input length; no network protocol or
certificate-handling path in OpenSSL exercises the overflow.
Triggering the bug requires an application that calls
ASN1_mbstring_copy() or ASN1_mbstring_ncopy() directly, or registers
a custom string type via ASN1_STRING_TABLE_add(), with
attacker-controlled input on the order of half a gigabyte or more.
For these reasons this issue was assigned Low severity.
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.
CVSS Score
8.1
EPSS Score
0.008
Published
2026-06-09
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 kek_unwrap_key().
Impact summary: A heap buffer over-read may trigger a crash which leads to
Denial of Service for an application if the input buffer ends at a memory
page boundary and the following page is unmapped. There is no information
disclosure as the over-read bytes are not revealed to the attacker.
The key unwrapping function performs a check-byte test as specified in the
RFC that reads 7 bytes from a heap allocation that is based on the wrapped
key length from the message. There is a minimum length check based on the
block length of the wrapping cipher. However the cipher is selected from
an OID carried in the attacker's PWRI keyEncryptionAlgorithm with no
requirement that the cipher be a block cipher. When an attacker selects
a stream-mode cipher the guard will be ineffective and the allocated buffer
containing the unwrapped key can be too small to fit the check-bytes
specified in the RFC and a buffer over-read can happen.
Applications calling CMS_decrypt() or CMS_decrypt_set1_password()
(equivalently openssl cms -decrypt -pwri_password ...) on untrusted CMS
data are vulnerable to this issue. No password knowledge is required: the
over-read happens during the unwrap attempt before any authentication
succeeds.
The over-read is limited to a few bytes and is not written to output, so
there is no information disclosure. Triggering a crash requires the
allocation to border unmapped memory, which is unlikely with the normal
allocator.
The FIPS modules are not affected by this issue.
CVSS Score
7.5
EPSS Score
0.007
Published
2026-06-09
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 PKCS7_verify(). 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
BIO_free() on the BIO originally passed to PKCS7_verify(). 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.
CVSS Score
8.8
EPSS Score
0.036
Published
2026-06-09
Issue summary: A specially crafted password-encrypted CMS message
can trigger a NULL pointer dereference during CMS decryption.
Impact summary: This NULL pointer dereference leads to an application crash
and a Denial of Service.
The CMS PasswordRecipientInfo.keyDerivationAlgorithm field is defined as
OPTIONAL in the ASN.1 specification and may therefore be absent in specially
crafted inputs. During the password-based CMS decryption the OpenSSL
CMS implementation dereferences this field without first checking whether it
was present.
An attacker who supplies such a CMS message to an application performing
password-based CMS decryption can trigger an application crash, leading to
a Denial of Service.
Applications that process password-encrypted CMS messages may be 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.
CVSS Score
5.9
EPSS Score
0.011
Published
2026-06-09
Issue summary: Parsing a crafted DER-encoded ASN.1 structure with a primitive
element whose content exceeds 2 gigabytes in length may cause a heap buffer
over-read on 64-bit Unix and Unix-like platforms.
Impact summary: The heap buffer over-read may crash the application (Denial of
Service) or to load into the decoded ASN.1 object contents of memory beyond the
end of the input buffer. More typically such ASN.1 elements would instead be
truncated.
An integer truncation in OpenSSL's ASN.1 decoder causes the content length of
an ASN.1 primitive element to be mishandled when it exceeds 2 gigabytes. In the
worst case the truncated length is treated as a request to scan the binary
content for a terminating zero byte, possibly causing OpenSSL to read either
less than or beyond the end of the allocated buffer.
Applications that pass attacker-supplied data to d2i_X509(), d2i_PKCS7(), or
any other d2i_* decoding function are affected. OpenSSL's own command-line
tools are not vulnerable, as data read through the BIO layer is checked before
it reaches the affected code. The issue only affects 64-bit Unix and Unix-like
platforms; 32-bit platforms and 64-bit Windows 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.
CVSS Score
7.5
EPSS Score
0.01
Published
2026-06-09
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 CMS_decrypt() 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.
CVSS Score
7.5
EPSS Score
0.008
Published
2026-04-07
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 CMS_decrypt() 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.
CVSS Score
7.5
EPSS Score
0.008
Published
2026-04-07
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.
CVSS Score
8.1
EPSS Score
0.007
Published
2026-04-07
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 X509_V_FLAG_USE_DELTAS flag to be enabled in
the verification context, the certificate being verified to contain a
freshestCRL extension or the base CRL to have the EXFLAG_FRESHEST 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.
CVSS Score
7.5
EPSS Score
0.009
Published
2026-04-07
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