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GO-2021-0160 CVE-2015-8618

Incorrect calculation affecting RSA computations in math/big

Not rated yet Go
Severity
Not rated yet
No source has published a CVSS score yet
Exploit chance (EPSS)
2.63%
Chance of exploitation in the next 30 days. Higher than 85.51% of scored vulnerabilities.
Known exploited
No
Not in CISA's catalog
Weakness
—
Not classified
Fix
1.5.3
Upgrade stdlib to this version or later

Description

Int.Exp Montgomery mishandled carry propagation and produced an incorrect output, which makes it easier for attackers to obtain private RSA keys via unspecified vectors.

This issue can affect RSA computations in crypto/rsa, which is used by crypto/tls. TLS servers on 32-bit systems could plausibly leak their RSA private key due to this issue. Other protocol implementations that create many RSA signatures could also be impacted in the same way.

Specifically, incorrect results in one part of the RSA Chinese Remainder computation can cause the result to be incorrect in such a way that it leaks one of the primes. While RSA blinding should prevent an attacker from crafting specific inputs that trigger the bug, on 32-bit systems the bug can be expected to occur at random around one in 2^26 times. Thus collecting around 64 million signatures (of known data) from an affected server should be enough to extract the private key used.

Note that on 64-bit systems, the frequency of the bug is so low (less than one in 2^50) that it would be very difficult to exploit.

Affected versions

Go

PackageVulnerableFixed in
stdlib
>= 1.5.0-0, < 1.5.3
1.5.3

How to fix

Move to the fixed version or later with your package manager, update the lockfile, and run your tests. If the package only arrives through another dependency, upgrade that dependency first. If none of its releases pulls a fixed version yet, force the version with your package manager's override.

stdlib Go → 1.5.3

go
go get stdlib@v1.5.3 && go mod tidy

References

Fixes and patches

Issue reports

Other links

Timeline

  1. Published
  2. Last updated by the source
  3. Latest EPSS score
AdvisorySeverityWhy it's related
GHSA-4374-p667-p6c8
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CVE-2020-0601
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RUSTSEC-2026-0382
Distrust compromised intermediate certificates in crypto/x509
Medium Also affects stdlib
GO-2026-6613
HTTP/1 server connection desynchronization after 2xx CONNECT response in net/http
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GO-2026-6609
Lack of limit on size of parsed Range headers in net/http
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GO-2026-6608
Memory limit bypass when parsing MIME headers in net/textproto, mime/multipart
High Also affects stdlib
GO-2026-6607
Reject malformed ECH outer extension references in crypto/tls
High Also affects stdlib
GO-2026-6604
Root.Mkdir(All) can follow junctions out of the root on Windows in os
Critical Also affects stdlib

Credits: Nick Craig-Wood

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