crypto/tls: Improper Certificate Validation
CVE-2025-68121 is a critical-severity improper certificate validation vulnerability in crypto/tls from Go standard library, with a CVSS 3.1 base score of 10.0 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 1.24.13, 1.25.7, 1.26.0-rc.3 as the first without the flaw, so updating crypto/tls to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.9% chance of exploitation within 30 days, higher than 60% of scored CVEs.
Critical severity: a successful attack would have severe impact.
What to do
- Update crypto/tls to 1.24.13 or 1.25.7 or 1.26.0-rc.3, whichever matches your release line, or a later version.
- Update Go to 1.24.13 or 1.25.7, whichever matches your release line, or a later version.
- Read the advisory on pkg.go.dev for workarounds and exact fixed builds.
- Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| Go standard library | crypto/tls | before 1.24.13; 1.25.0-0 up to, but not including, 1.25.7; 1.26.0-rc.1 up to, but not including, 1.26.0-rc.3 | 1.24.13, 1.25.7, 1.26.0-rc.3 |
| Go | Go | before 1.24.13; 1.25.0 up to, but not including, 1.25.7; 1.26.0 | 1.24.13, 1.25.7 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- NoneNo account or login is needed.
- User interaction
- NoneNo action by a victim is required.
- Scope
- ChangedThe attack can reach beyond the vulnerable component into other systems.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- HighData or code can be modified at will.
- Availability
- HighThe component can be taken down completely.
Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:H/A:H. Scored by NVD.
| Scoring system | Score | Severity | Scored by |
|---|---|---|---|
| CVSS 3.1 | 10.0 | Critical | NVD |
| CVSS 3.1 | 9.1 | Critical | CISA (ADP) |
Official description
During session resumption in crypto/tls, if the underlying Config has its ClientCAs or RootCAs fields mutated between the initial handshake and the resumed handshake, the resumed handshake may succeed when it should have failed. This may happen when a user calls Config.Clone and mutates the returned Config, or uses Config.GetConfigForClient. This can cause a client to resume a session with a server that it would not have resumed with during the initial handshake, or cause a server to resume a session with a client that it would not have resumed with during the initial handshake.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Improper Certificate Validation
The product does not validate, or incorrectly validates, a certificate.
How developers prevent this class of flaw
- Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.
- If certificate pinning is being used, ensure that all relevant properties of the certificate are fully validated before the certificate is pinned, including the hostname.
More Improper Certificate Validation vulnerabilities (CWE-295)
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: total).
- Record last changed materially (score, affected products, status or references).
References
Advisories
Patches and release notes
Third-party and government advisories
- groups.google.com/g/golang-announce/c/K09ubi9FQFkMailing List, Third Party Advisory
Technical write-ups (may include proof of concept)
- go.dev/issue/77217Exploit, Issue Tracking
Other vulnerabilities in crypto/tls
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
- 7.5 High severity
Recent Improper Certificate Validation vulnerabilities
- 8.8 High severity
- 7.4 High severity
- 8.1 High severity
- 8.1 High severity
- 7.7 High severity
- 9.3 Critical severity
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