Python 2 Security Vulnerability (CVE) Updates
As part of ActiveState’s Python 2 extended support, we continuously evaluate known security vulnerabilities (CVE’s) impacting Python 2.7 since Python 2 End of Life (EOL) occurred on January 1, 2020, including vulnerabilities to both the core language and third-party packages.
Python 2 EOL is of particular concern for PCI-DSS and other data security standards regarding payment processing data, where you must be able to identify security vulnerabilities using reputable outside sources (PCI-DSS 6.1), and protect all system components and software from known vulnerabilities by installing applicable security patches (PCI-DSS 6.2).
The following CVE’s can be reviewed for your own internal remediation via the links below. Alternatively, ActiveState has released fixes for these vulnerabilities in Python 2.7.18, available for enterprise builds with our Python 2 extended support options.
|CVE||Severity||Package Description||Status||Publish Date|
The package python/cpython from 0 and before 3.6.13, from 3.7.0 and before 3.7.10, from 3.8.0 and before 3.8.8, from 3.9.0 and before 3.9.2 are vulnerable to Web Cache Poisoning via urllib.parse.parse_qsl and urllib.parse.parse_qs by using a vector called parameter cloaking. When the attacker can separate query parameters using a semicolon (;), they can cause a difference in the interpretation of the request between the proxy (running with default configuration) and the server. This can result in malicious requests being cached as completely safe ones, as the proxy would usually not see the semicolon as a separator, and therefore would not include it in a cache key of an unkeyed parameter.
|CVE-2021-3177||Critical||Python 3.x through 3.9.1 has a buffer overflow in PyCArg_repr in _ctypes/callproc.c, which may lead to remote code execution in certain Python applications that accept floating-point numbers as untrusted input, as demonstrated by a 1e300 argument to c_double.from_param. This occurs because sprintf is used unsafely. The same buffer overflow issue is present in Python 184.108.40.206 (and earlier 2.7.18 versions) and when hit will panic a running python process.||Fix available||2021/01/19|
|CVE-2020-27619||Critical||In Python 3 through 3.9.0, the Lib/test/multibytecodec_support.py CJK codec tests call eval() on content retrieved via HTTP. Although the code is different between Python 2 and Python 3, the same issue with the eval() is present in Python 2.7.18.||Fix available||2020/10/21|
|CVE-2020-26116||High||http.client in Python 3.x before 3.5.10, 3.6.x before 3.6.12, 3.7.x before 3.7.9, and 3.8.x before 3.8.5 allows CRLF injection if the attacker controls the HTTP request method, inserting CR and LF control characters in the first argument of HTTPConnection.request. Although the httplib module is laid out differently in Python 3, the same execution path and behaviour is present in Python 2.7.18.||Fix available||2020/09/27|
|CVE-2019-20907||High||In Lib/tarfile.py in Python through 3.8.3, an attacker is able to craft a TAR archive leading to an infinite loop when opened by tarfile.open, because _proc_pax lacks header validation.||Fix available||2020/07/13|
|CVE-2020-8492||Medium||Core library urllib allows an HTTP server to conduct Regular Expression Denial of Service (ReDoS) attacks against a client.||Fix available||2020/01/30|
Third-Party Package Vulnerabilities
|CVE||Severity||Package Description||Status||Publish Date|
lxml is a library for processing XML and HTML in the Python language. Prior to version 4.6.5, the HTML Cleaner in lxml.html lets certain crafted script content pass through, as well as script content in SVG files embedded using data URIs. Users that employ the HTML cleaner in a security relevant context should upgrade to lxml 4.6.5 to receive a patch. There are no known workarounds available.
OpenSSL – In order to decrypt SM2 encrypted data an application is expected to call the API function EVP_PKEY_decrypt(). Typically an application will call this function twice. The first time, on entry, the “out” parameter can be NULL and, on exit, the “outlen” parameter is populated with the buffer size required to hold the decrypted plaintext. The application can then allocate a sufficiently sized buffer and call EVP_PKEY_decrypt() again, but this time passing a non-NULL value for the “out” parameter. A bug in the implementation of the SM2 decryption code means that the calculation of the buffer size required to hold the plaintext returned by the first call to EVP_PKEY_decrypt() can be smaller than the actual size required by the second call….
An issue was discovered in Pillow before 8.1.1. TiffDecode has a heap-based buffer overflow when decoding crafted YCbCr files because of certain interpretation conflicts with LibTIFF in RGBA mode. NOTE: this issue exists because of an incomplete fix for CVE-2020-35654.
OpenSSL – ASN.1 strings are represented internally within OpenSSL as an ASN1_STRING structure which contains a buffer holding the string data and a field holding the buffer length. This contrasts with normal C strings which are repesented as a buffer for the string data which is terminated with a NUL (0) byte. Although not a strict requirement, ASN.1 strings that are parsed using OpenSSL’s own “d2i” functions (and other similar parsing functions) as well as any string whose value has been set with the ASN1_STRING_set() function will additionally NUL terminate the byte array in the ASN1_STRING structure. However, it is possible for applications to directly construct valid ASN1_STRING structures which do not NUL terminate the byte array by directly setting the “data”…
Django before 2.2.24, 3.x before 3.1.12, and 3.2.x before 3.2.4 has a potential directory traversal via django.contrib.admindocs. Staff members could use the TemplateDetailView view to check the existence of arbitrary files. Additionally, if (and only if) the default admindocs templates have been customized by application developers to also show file contents, then not only the existence but also the file contents would have been exposed. In other words, there is directory traversal outside of the template root directories.
In Django 2.2 before 2.2.21, 3.1 before 3.1.9, and 3.2 before 3.2.1, MultiPartParser, UploadedFile, and FieldFile allowed directory traversal via uploaded files with suitably crafted file names.
An infinite loop in SMLLexer in Pygments versions 1.5 to 2.7.3 may lead to denial of service when performing syntax highlighting of a Standard ML (SML) source file, as demonstrated by input that only contains the “exception” keyword.
|Fix in progress||2021/03/23|
An OpenSSL TLS server may crash if sent a maliciously crafted renegotiation ClientHello message from a client. If a TLSv1.2 renegotiation ClientHello omits the signature_algorithms extension (where it was present in the initial ClientHello), but includes a signature_algorithms_cert extension then a NULL pointer dereference will result, leading to a crash and a denial of service attack. A server is only vulnerable if it has TLSv1.2 and renegotiation enabled (which is the default configuration). OpenSSL TLS clients are not impacted by this issue. All OpenSSL 1.1.1 versions are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1k. OpenSSL 1.0.2 is not impacted by this issue. Fixed in OpenSSL 1.1.1k (Affected 1.1.1-1.1.1j).
The X509_V_FLAG_X509_STRICT flag enables additional security checks of the certificates present in a certificate chain. It is not set by default. Starting from OpenSSL version 1.1.1h a check to disallow certificates in the chain that have explicitly encoded elliptic curve parameters was added as an additional strict check. An error in the implementation of this check meant that the result of a previous check to confirm that certificates in the chain are valid CA certificates was overwritten. This effectively bypasses the check that non-CA certificates must not be able to issue other certificates. If a “purpose” has been configured then there is a subsequent opportunity for checks that the certificate is a valid CA. All of the named “purpose” values implemented in libcrypto perform this check. Therefore, where a purpose is set the certificate chain will still be rejected even when the strict flag has been used. A purpose is set by default in libssl client and server certificate verification routines, but it can be overridden or removed by an application. In order to be affected, an application must explicitly set the X509_V_FLAG_X509_STRICT verification flag and either not set a purpose for the certificate verification or, in the case of TLS client or server applications, override the default purpose. OpenSSL versions 1.1.1h and newer are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1k. OpenSSL 1.0.2 is not impacted by this issue. Fixed in OpenSSL 1.1.1k (Affected 1.1.1h-1.1.1j).
The OpenSSL public API function X509_issuer_and_serial_hash() attempts to create a unique hash value based on the issuer and serial number data contained within an X509 certificate. However it fails to correctly handle any errors that may occur while parsing the issuer field (which might occur if the issuer field is maliciously constructed). This may subsequently result in a NULL pointer deref and a crash leading to a potential denial of service attack. The function X509_issuer_and_serial_hash() is never directly called by OpenSSL itself so applications are only vulnerable if they use this function directly and they use it on certificates that may have been obtained from untrusted sources. OpenSSL versions 1.1.1i and below are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1j. OpenSSL versions 1.0.2x and below are affected by this issue. However OpenSSL 1.0.2 is out of support and no longer receiving public updates. Premium support customers of OpenSSL 1.0.2 should upgrade to 1.0.2y. Other users should upgrade to 1.1.1j. Fixed in OpenSSL 1.1.1j (Affected 1.1.1-1.1.1i). Fixed in OpenSSL 1.0.2y (Affected 1.0.2-1.0.2x).
Calls to EVP_CipherUpdate, EVP_EncryptUpdate and EVP_DecryptUpdate may overflow the output length argument in some cases where the input length is close to the maximum permissable length for an integer on the platform. In such cases the return value from the function call will be 1 (indicating success), but the output length value will be negative. This could cause applications to behave incorrectly or crash. OpenSSL versions 1.1.1i and below are affected by this issue. Users of these versions should upgrade to OpenSSL 1.1.1j. OpenSSL versions 1.0.2x and below are affected by this issue. However OpenSSL 1.0.2 is out of support and no longer receiving public updates. Premium support customers of OpenSSL 1.0.2 should upgrade to 1.0.2y. Other users should upgrade to 1.1.1j. Fixed in OpenSSL 1.1.1j (Affected 1.1.1-1.1.1i). Fixed in OpenSSL 1.0.2y (Affected 1.0.2-1.0.2x).
|CVE-2020-36242||Critical||In the cryptography package before 3.3.2 for Python, certain sequences of update calls to symmetrically encrypt multi-GB values could result in an integer overflow and buffer overflow, as demonstrated by the Fernet class.||Fix available||2021/02/07|
In Pillow before 8.1.0, TiffDecode has a heap-based buffer overflow when decoding crafted YCbCr files because of certain interpretation conflicts with LibTIFF in RGBA mode.
|CVE-2019-11068||Critical||libxslt through 1.1.33 allows bypass of a protection mechanism because callers of xsltCheckRead and xsltCheckWrite permit access even upon receiving a -1 error code. xsltCheckRead can return -1 for a crafted URL that is not actually invalid and is subsequently loaded.||Fix available||2020/04/10|
|CVE-2020-7212||High||The _encode_invalid_chars function in util/url.py in the urllib3 library 1.25.2 through 1.25.7 for Python allows a denial of service (CPU consumption) because of an inefficient algorithm. The percent_encodings array contains all matches of percent encodings. It is not deduplicated. For a URL of length N, the size of percent_encodings may be up to O(N). The next step (normalize existing percent-encoded bytes) also takes up to O(N) for each step, so the total time is O(N^2). If percent_encodings were deduplicated, the time to compute _encode_invalid_chars would be O(kN), where k is at most 484 ((10+6*2)^2).||Fix available||2020/03/06|
|CVE-2020-26137||Medium||urllib3 before 1.25.9 allows CRLF injection if the attacker controls the HTTP request method, as demonstrated by inserting CR and LF control characters in the first argument of putrequest(). NOTE: this is similar to CVE-2020-26116.||Fix available||2020/09/30|
|CVE-2020-5390||High||PySAML2 before 5.0.0 does not check that the signature in a SAML document is enveloped and thus signature wrapping is effective, i.e., it is affected by XML Signature Wrapping (XSW). The signature information and the node/object that is signed can be in different places and thus the signature verification will succeed, but the wrong data will be used. This specifically affects the verification of assertion that has been signed.||Fix available||2020/01/13|
In libImaging/SgiRleDecode.c in Pillow through 7.0.0, a number of out-of-bounds reads exist in the parsing of SGI image files, a different issue than CVE-2020-5311.
Lib/ipaddress.py in Python through 3.8.3 improperly computes hash values in the IPv4Interface and IPv6Interface classes, which might allow a remote attacker to cause a denial of service if an application is affected by the performance of a dictionary containing IPv4Interface or IPv6Interface objects, and this attacker can cause many dictionary entries to be created.
NOTE: ipaddress is a backported Python 2 library from Python 3 core and is vulnerable to the issue described. ActiveState has forked this version and fixed it. Source is available in our public Github repository.
|CVE-2020-11655||High||SQLite through 3.31.1 allows attackers to cause a denial of service (segmentation fault) via a malformed window-function query because the AggInfo object’s initialization is mishandled.||Fix available||2020/04/08|
|CVE-2020-6802||Medium||In Mozilla Bleach before 3.11, a mutation XSS affects users calling bleach.clean with noscript and a raw tag in the allowed/whitelisted tags option.||Fix available||2020/03/24|
|CVE-2020-5313||High||libImaging/FliDecode.c in Pillow before 6.2.2 has an FLI buffer overflow.||Fix available||2020/01/02|
|CVE-2020-5312||Critical||libImaging/PcxDecode.c in Pillow before 6.2.2 has a PCX P mode buffer overflow.||Fix available||2020/01/02|
|CVE-2020-5311||Critical||libImaging/SgiRleDecode.c in Pillow before 6.2.2 has an SGI buffer overflow.||Fix available||2020/01/02|
|CVE-2020-5310||High||libImaging/TiffDecode.c in Pillow before 6.2.2 has a TIFF decoding integer overflow, related to realloc.||Fix available||2020/01/02|
In libexpat in Expat before 2.2.7, XML input including XML names that contain a large number of colons could make the XML parser consume a high amount of RAM and CPU resources while processing (enough to be usable for denial-of-service attacks).
BZ2_decompress in decompress.c in bzip2 through 1.0.6 has an out-of-bounds write when there are many selectors.
In addition, we open source all of our fixes in our public GitHub repo in order to allow the community to review and incorporate them into their projects.