CVE-2020-0601, aka NSACrypt

A spoofing vulnerability exists in the way Windows CryptoAPI (Crypt32.dll) validates Elliptic Curve Cryptography (ECC) certificates.An attacker could exploit the vulnerability by using a spoofed code-signing certificate to sign a malicious executable, making it appear the file was from a trusted, legitimate source, aka ‘Windows CryptoAPI Spoofing Vulnerability’.

Recent assessments:

busterb at January 14, 2020 8:26pm UTC reported:

I’m not so sure that @todb-r7’s assessment is completely correct, this affects all the things that validate certs, including TLS in browsers, powershell, etc. So kinda impactful beyond just local code execution, this could be a vector for all kinds of other spoofing.

More info in swiftonsecurity’s thread regarding how this pivots into RCE: <https://threadreaderapp.com/thread/1217159419533893633.html&gt;

The method that should be affected here is <https://docs.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-certgetcertificatechain&gt; courtesy of <https://twitter.com/hackerfantastic/status/1217211301375696896&gt;

Open source software that uses or exposes this method: https://codesearch.debian.net/search?q=CertGetCertificateChain&literal=1

The exposure of user-defined eliptical curves in TLS certificates created a window of opportunity for this bug to appear, which may have been mitigated if the underlying specification was simpler as well, especially with regards to seldom-used features like this. One may want to look ahead to similar bugs in other dark corners of a TLS implementation near you!

jcran at January 16, 2020 12:31am UTC reported:

I’m not so sure that @todb-r7’s assessment is completely correct, this affects all the things that validate certs, including TLS in browsers, powershell, etc. So kinda impactful beyond just local code execution, this could be a vector for all kinds of other spoofing.

More info in swiftonsecurity’s thread regarding how this pivots into RCE: <https://threadreaderapp.com/thread/1217159419533893633.html&gt;

The method that should be affected here is <https://docs.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-certgetcertificatechain&gt; courtesy of <https://twitter.com/hackerfantastic/status/1217211301375696896&gt;

Open source software that uses or exposes this method: https://codesearch.debian.net/search?q=CertGetCertificateChain&literal=1

The exposure of user-defined eliptical curves in TLS certificates created a window of opportunity for this bug to appear, which may have been mitigated if the underlying specification was simpler as well, especially with regards to seldom-used features like this. One may want to look ahead to similar bugs in other dark corners of a TLS implementation near you!

todb-r7 at January 14, 2020 8:20pm UTC reported:

I’m not so sure that @todb-r7’s assessment is completely correct, this affects all the things that validate certs, including TLS in browsers, powershell, etc. So kinda impactful beyond just local code execution, this could be a vector for all kinds of other spoofing.

More info in swiftonsecurity’s thread regarding how this pivots into RCE: <https://threadreaderapp.com/thread/1217159419533893633.html&gt;

The method that should be affected here is <https://docs.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-certgetcertificatechain&gt; courtesy of <https://twitter.com/hackerfantastic/status/1217211301375696896&gt;

Open source software that uses or exposes this method: https://codesearch.debian.net/search?q=CertGetCertificateChain&literal=1

The exposure of user-defined eliptical curves in TLS certificates created a window of opportunity for this bug to appear, which may have been mitigated if the underlying specification was simpler as well, especially with regards to seldom-used features like this. One may want to look ahead to similar bugs in other dark corners of a TLS implementation near you!

bwatters-r7 at January 23, 2020 8:45pm UTC reported:

I’m not so sure that @todb-r7’s assessment is completely correct, this affects all the things that validate certs, including TLS in browsers, powershell, etc. So kinda impactful beyond just local code execution, this could be a vector for all kinds of other spoofing.

More info in swiftonsecurity’s thread regarding how this pivots into RCE: <https://threadreaderapp.com/thread/1217159419533893633.html&gt;

The method that should be affected here is <https://docs.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-certgetcertificatechain&gt; courtesy of <https://twitter.com/hackerfantastic/status/1217211301375696896&gt;

Open source software that uses or exposes this method: https://codesearch.debian.net/search?q=CertGetCertificateChain&literal=1

The exposure of user-defined eliptical curves in TLS certificates created a window of opportunity for this bug to appear, which may have been mitigated if the underlying specification was simpler as well, especially with regards to seldom-used features like this. One may want to look ahead to similar bugs in other dark corners of a TLS implementation near you!

hrbrmstr at January 15, 2020 7:16pm UTC reported:

I’m not so sure that @todb-r7’s assessment is completely correct, this affects all the things that validate certs, including TLS in browsers, powershell, etc. So kinda impactful beyond just local code execution, this could be a vector for all kinds of other spoofing.

More info in swiftonsecurity’s thread regarding how this pivots into RCE: <https://threadreaderapp.com/thread/1217159419533893633.html&gt;

The method that should be affected here is <https://docs.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-certgetcertificatechain&gt; courtesy of <https://twitter.com/hackerfantastic/status/1217211301375696896&gt;

Open source software that uses or exposes this method: https://codesearch.debian.net/search?q=CertGetCertificateChain&literal=1

The exposure of user-defined eliptical curves in TLS certificates created a window of opportunity for this bug to appear, which may have been mitigated if the underlying specification was simpler as well, especially with regards to seldom-used features like this. One may want to look ahead to similar bugs in other dark corners of a TLS implementation near you!

wvu-r7 at January 15, 2020 12:29am UTC reported:

I’m not so sure that @todb-r7’s assessment is completely correct, this affects all the things that validate certs, including TLS in browsers, powershell, etc. So kinda impactful beyond just local code execution, this could be a vector for all kinds of other spoofing.

More info in swiftonsecurity’s thread regarding how this pivots into RCE: <https://threadreaderapp.com/thread/1217159419533893633.html&gt;

The method that should be affected here is <https://docs.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-certgetcertificatechain&gt; courtesy of <https://twitter.com/hackerfantastic/status/1217211301375696896&gt;

Open source software that uses or exposes this method: https://codesearch.debian.net/search?q=CertGetCertificateChain&literal=1

The exposure of user-defined eliptical curves in TLS certificates created a window of opportunity for this bug to appear, which may have been mitigated if the underlying specification was simpler as well, especially with regards to seldom-used features like this. One may want to look ahead to similar bugs in other dark corners of a TLS implementation near you!

gwillcox-r7 at October 20, 2020 7:04pm UTC reported:

I’m not so sure that @todb-r7’s assessment is completely correct, this affects all the things that validate certs, including TLS in browsers, powershell, etc. So kinda impactful beyond just local code execution, this could be a vector for all kinds of other spoofing.

More info in swiftonsecurity’s thread regarding how this pivots into RCE: <https://threadreaderapp.com/thread/1217159419533893633.html&gt;

The method that should be affected here is <https://docs.microsoft.com/en-us/windows/win32/api/wincrypt/nf-wincrypt-certgetcertificatechain&gt; courtesy of <https://twitter.com/hackerfantastic/status/1217211301375696896&gt;

Open source software that uses or exposes this method: https://codesearch.debian.net/search?q=CertGetCertificateChain&literal=1

The exposure of user-defined eliptical curves in TLS certificates created a window of opportunity for this bug to appear, which may have been mitigated if the underlying specification was simpler as well, especially with regards to seldom-used features like this. One may want to look ahead to similar bugs in other dark corners of a TLS implementation near you!

Assessed Attacker Value: 5
Assessed Attacker Value: 5Assessed Attacker Value: 3