CVE-2025-68121VulnerabilityPublished 5 Feb 2026Updated 29 Apr 2026

CVE-2025-68121: Go standard library crypto/tls · Improper Certificate Validation

Affects Go standard library crypto/tlsSource CVE Database V5

Not known to be exploited · CVSS 9.1 Critical · fixed in 1.26.0-rc.3 : patch Go standard library crypto/tls as a priority.

Data as of 26 Oct 2026, 07:57 UTC

CVSS 3.1 base score

9.1Critical

How severe the flaw is on the 0–10 CVSS scale.

EPSS: 0.9% chance of exploitation in 30 days – higher than 59% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.26.0-rc.3, 1.25.7, 1.24.13

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N

Attack Vector: Network
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: High
Integrity: High
Availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable component is bound to the network stack and the set of possible attackers extends beyond the other options listed, up to and including the entire Internet. Such a vulnerability is often termed 'remotely exploitable' and can be thought of as an attack being exploitable at the protocol level one or more network hops away (e.g., across one or more routers).
Attack Complexity: Low: Specialized access conditions or extenuating circumstances do not exist. An attacker can expect repeatable success against the vulnerable component.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without any interaction from any user.
Scope: Unchanged: An exploited vulnerability can only affect resources managed by the same security authority. In this case, the vulnerable component and the impacted component are either the same, or both are managed by the same security authority.
Confidentiality: High: There is total loss of confidentiality, resulting in all resources within the impacted component being divulged to the attacker. Alternatively, access to only some restricted information is obtained, but the disclosed information presents a direct, serious impact.
Integrity: High: There is a total loss of integrity, or a complete loss of protection. For example, the attacker is able to modify any/all files protected by the impacted component. Alternatively, only some files can be modified, but malicious modification would present a direct, serious consequence to the impacted component.
Availability: None: There is no impact to availability within the impacted component.

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 5 Feb 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponised: no evidence on record.
No public exploit code indexed in Metasploit or Exploit-DB
Exploited in the wildExploited: no evidence on record.
Not in CISA KEV and no source reports exploitation
Observed by OffSeq MirageSeen by Mirage: no evidence on record.
No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 2026-10-26.

Disclosed: The CVE record is public on cve.org. Its publication is t = 0.
Detectable: A public nuclei template can find exposed instances, for defenders and attackers alike.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, or CISA SSVC reports a public proof of concept.
Exploited in the wild: CISA KEV lists it, CISA SSVC rates exploitation active, or a source reports attacks.
Observed by OffSeq Mirage: OffSeq Mirage honeypot sensors recorded attack traffic for this CVE, or found exposed hosts without attack traffic.

Moments are spaced evenly, not to scale; a dashed line marks a gap of six months or more. Deltas count from t = 0. Sources that give only a date (CISA KEV, Exploit-DB, or a time of exactly 00:00Z) read “same day” rather than hours. Metasploit modules carry the flaw’s disclosure date, not their release date, and nuclei templates carry no date, so both appear above but not on the timeline.

What to do

Upgrade Go standard library crypto/tls to 1.26.0-rc.3, 1.25.7 or 1.24.13.

Affected software

Product	Affected	Fixed in
Go standard librarycrypto/tls	Affected <1.24.13 >=1.25.0-0 <1.25.7 >=1.26.0-rc.1 <1.26.0-rc.3	Fixed in 1.26.0-rc.3 1.25.7 1.24.13
Gocrypto/tls`pkg:golang/crypto/tls`Other threats	Affected <1.24.13 >=1.25.0-0 <1.25.7 >=1.26.0-rc.1 <1.26.0-rc.3	Fixed in 1.24.13 1.25.7 1.26.0-rc.3
Gogithub.com/golang/go/src/crypto/tls`pkg:golang/github.com/golang/go/src/crypto/tls`Other threats	Affected =0 =1.25.0-0 =1.26.0-rc.1	Fixed in–

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

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.

Impact

The vulnerability can allow an attacker to bypass intended certificate validation during TLS session resumption, potentially enabling unauthorized session resumption with a client or server that would have been rejected during the initial handshake. This undermines the security guarantees of TLS authentication, risking confidentiality and integrity of communications. There are no known exploits in the wild as of the published date.

Summary

This vulnerability arises from improper validation of certificates during TLS session resumption in Go's crypto/tls library. Specifically, if the TLS Config's ClientCAs or RootCAs fields are changed after the initial handshake but before resumption, the resumed handshake may incorrectly succeed. This is due to the resumed handshake relying on the mutated Config rather than the original validation context. The issue affects Go versions prior to 1.26.0-rc.1 and can lead to resumed sessions with entities that would have been rejected initially, violating expected authentication constraints. The CVSS v3.1 score is 9.1 (critical) with network attack vector, low complexity, no privileges or user interaction required, and high confidentiality and integrity impact.

CWE-295Improper Certificate Validation (opens in a new tab)
Base weaknessOWASP Top 10 A07:2025: Authentication Failures (opens in a new tab)
The product does not validate, or incorrectly validates, a certificate.
Architecture and Design · Implementation
Certificates should be carefully managed and checked to assure that data are encrypted with the intended owner's public key.
Implementation
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.
OWASP Cheat Sheets
Transport Layer Protection (opens in a new tab)
TLS Cipher String (opens in a new tab)
OWASP Authentication (opens in a new tab)
OWASP ASVS 4.0.3
V9.2.1 (opens in a new tab)
V1.9.2 (opens in a new tab)
V2.8.5 (opens in a new tab)
Attack patterns
Creating a Rogue Certification Authority Certificate (opens in a new tab)
Signature Spoofing by Improper Validation (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 30 Apr 2026, 02:02 UTC

WeaknessesCWE-295

Technical details

References

Community reviews

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