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crypto/x509: excluded subdomain constraint doesn't preclude wildcard SAN (CVE-2025-61727) #76442

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crypto/x509: excluded subdomain constraint doesn't preclude wildcard SAN (CVE-2025-61727)#76442
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rolandshoemaker
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FixPendingIssues that have a fix which has not yet been reviewed or submitted.NeedsFixThe path to resolution is known, but the work has not been done.Securityrelease-blocker
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Go1.26

Description

@rolandshoemaker
rolandshoemaker
opened on Nov 24, 2025

A certificate with the excluded constraint foo.example.com should preclude a leaf with the SAN *.example.com. This unfortunately is not well defined in the X.509 specifications, so slipped through.

This is a PUBLIC track security issue.

Activity

  1. rolandshoemaker
    self-assigned this
    on Nov 24, 2025
  2. rolandshoemaker
    added
    Security
    on Nov 24, 2025

  3. gopherbot commented on Nov 24, 2025

    @gopherbot
    gopherbot
    on Nov 24, 2025
    Contributor

    Change https://go.dev/cl/723900 mentions this issue: crypto/x509: excluded subdomain constraints preclude wildcard SANs

  4. rolandshoemaker commented on Nov 25, 2025

    @rolandshoemaker
    rolandshoemaker
    on Nov 25, 2025
    MemberAuthor

    @gopherbot please open backport issues, this is a minor security bug.

  5. gopherbot commented on Nov 25, 2025

    @gopherbot
    gopherbot
    on Nov 25, 2025
    Contributor

    Backport issue(s) opened: #76463 (for 1.24), #76464 (for 1.25).

    Remember to create the cherry-pick CL(s) as soon as the patch is submitted to master, according to https://go.dev/wiki/MinorReleases.

  6. gopherbot commented on Nov 25, 2025

    @gopherbot
    gopherbot
    on Nov 25, 2025
    Contributor

    Change https://go.dev/cl/724400 mentions this issue: [release-branch.go1.25] crypto/x509: excluded subdomain constraints preclude wildcard SANs

  7. gopherbot commented on Nov 25, 2025

    @gopherbot
    gopherbot
    on Nov 25, 2025
    Contributor

    Change https://go.dev/cl/724401 mentions this issue: [release-branch.go1.24] crypto/x509: excluded subdomain constraints preclude wildcard SANs

  8. cherrymui
    added this to the Go1.26 milestone on Nov 25, 2025
  9. cherrymui
    added
    NeedsFixThe path to resolution is known, but the work has not been done.
    on Nov 25, 2025
  10. gopherbot
    added 2 commits that reference this issue on Nov 25, 2025

    [release-branch.go1.25] crypto/x509: excluded subdomain constraints p…

    287017a

    [release-branch.go1.24] crypto/x509: excluded subdomain constraints p…

    04db77a
  11. dmitshur
    added
    release-blocker
    FixPendingIssues that have a fix which has not yet been reviewed or submitted.
    on Nov 26, 2025
  12. dmitshur
    changed the title [-]crypto/x509: excluded subdomain constraint doesn't preclude wildcard SAN[/-] [+]crypto/x509: excluded subdomain constraint doesn't preclude wildcard SAN (CVE-2025-61727)[/+] on Dec 2, 2025

  13. dmitshur commented on Dec 2, 2025

    @dmitshur
    dmitshur
    on Dec 2, 2025
    Member

    @rolandshoemaker Checking on the status here, what is left to resolve this issue (for Go 1.26)? Thanks.

  14. rolandshoemaker commented on Dec 2, 2025

    @rolandshoemaker
    rolandshoemaker
    on Dec 2, 2025
    MemberAuthor

    We landed a different fix for this than was backported (I actually meant to land this first, and then the follow-up, but it auto-submitted before I noticed). This can be closed now since there is nothing left to do for 1.26.

  15. rolandshoemaker
    closed this as completedon Dec 2, 2025

  16. stapelberg commented on Dec 3, 2025

    @stapelberg
    stapelberg
    on Dec 3, 2025
    Contributor

    We landed a different fix for this than was backported (I actually meant to land this first, and then the follow-up, but it auto-submitted before I noticed). This can be closed now since there is nothing left to do for 1.26.

    Just for the record, the “different fix” is https://go.dev/cl/711421

  17. yiminc
    added a commit that references this issue on Jan 20, 2026

    Upgrade Go to 1.25.5 to fix crypto/x509 CVEs (#9073)

    cabbefa
  18. simvlad
    added a commit that references this issue on Jan 27, 2026

    Upgrade Go to 1.25.5 to fix crypto/x509 CVEs (#9073)

    c5ed97f
  19. lxq015
    added 2 commits that reference this issue on Mar 19, 2026

    [release-branch.go1.25] crypto/x509: excluded subdomain constraints p…

    aa2bb6c

    [release-branch.go1.25] crypto/x509: excluded subdomain constraints p…

    b676504
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