[security] Go 1.15.5 and Go 1.14.12 are released

[Katie Hockman]

Hi gophers,

We have just released Go 1.15.5 and Go 1.14.12 to address recently reported security issues. We recommend that all users update to one of these releases (if you’re not sure which, choose Go 1.15.5).

• math/big: panic during recursive division of very large numbers

A number of math/big.Int methods (Div, Exp, DivMod, Quo, Rem, QuoRem, Mod, ModInverse, ModSqrt, Jacobi, and GCD) can panic when provided crafted large inputs. For the panic to happen, the divisor or modulo argument must be larger than 3168 bits (on 32-bit architectures) or 6336 bits (on 64-bit architectures). Multiple math/big.Rat methods are similarly affected.

crypto/rsa.VerifyPSS, crypto/rsa.VerifyPKCS1v15, and crypto/dsa.Verify may panic when provided crafted public keys and signatures. crypto/ecdsa and crypto/elliptic operations may only be affected if custom CurveParams with unusually large field sizes (several times larger than the largest supported curve, P-521) are in use. Using crypto/x509.Verify on a crafted X.509 certificate chain can lead to a panic, even if the certificates don’t chain to a trusted root. The chain can be delivered via a crypto/tls connection to a client, or to a server that accepts and verifies client certificates. net/http clients can be made to crash by an HTTPS server, while net/http servers that accept client certificates will recover the panic and are unaffected.

Moreover, an application might crash invoking crypto/x509.(*CertificateRequest).CheckSignature on an X.509 certificate request or during a golang.org/x/crypto/otr conversation. Parsing a golang.org/x/crypto/openpgp Entity or verifying a signature may crash. Finally, a golang.org/x/crypto/ssh client can panic due to a malformed host key, while a server could panic if either PublicKeyCallback accepts a malformed public key, or if IsUserAuthority accepts a certificate with a malformed public key.

Thanks to the Go Ethereum team and the OSS-Fuzz project for reporting this. Thanks to Rémy Oudompheng and Robert Griesemer for their help developing and validating the fix.

This issue is CVE-2020-28362 and Go issue golang.org/issue/42552.

• cmd/go: arbitrary code execution at build time through cgo

The go command may execute arbitrary code at build time when cgo is in use. This may occur when running go get on a malicious package, or any other command that builds untrusted code.

This can be caused by malicious gcc flags specified via a #cgo directive, or by a malicious symbol name in a linked object file.

Thanks to Imre Rad and to Chris Brown and Tempus Ex respectively for reporting these issues.

These issues are CVE-2020-28367 and CVE-2020-28366, and Go issues golang.org/issue/42556 and golang.org/issue/42559 respectively.

Downloads are available at https://golang.org/dl for all supported platforms.

Thank you,
Katie on behalf of the Go team