VulnerabilityPublished 6 Mar 2026Updated 9 Mar 2026

CVE-2026-27139: Go standard library os · Race Condition Enabling Link Following

Affects Go standard library osSource CVE Database V5

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Not known to be exploited · CVSS 2.5 Low : upgrade to 1.26.1 or 1.25.8 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

2.5Low

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 11% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.26.1, 1.25.8

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

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

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

Attack Vector: Local: The vulnerable component is not bound to the network stack and the attacker’s path is via read/write/execute capabilities. Either: the attacker exploits the vulnerability by accessing the target system locally (e.g., keyboard, console), or remotely (e.g., SSH); or the attacker relies on User Interaction by another person to perform actions required to exploit the vulnerability (e.g., tricking a legitimate user into opening a malicious document).
Attack Complexity: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
Privileges Required: Low: The attacker is authorized with (i.e., requires) privileges that provide basic user capabilities that could normally affect only settings and files owned by a user. Alternatively, an attacker with Low privileges may have the ability to cause an impact only to non-sensitive resources.
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: Low: There is some loss of confidentiality. Access to some restricted information is obtained, but the attacker does not have control over what information is obtained, or the amount or kind of loss is limited. The information disclosure does not cause a direct, serious loss to the impacted component.
Integrity: None: There is no loss of integrity within 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 6 Mar 2026
Detectable: no evidence on record.
No public nuclei template indexed
Weaponized: 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 30 Oct 2026.

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.
Weaponized: A Metasploit exploit module or Exploit-DB entry exists (Metasploit scanner modules do not count), or CISA SSVC or the CVSS exploit maturity 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 os to 1.26.1 or 1.25.8.

Affected software

Product	Affected	Fixed in
Go standard libraryos	Affected >=1.26.0-0 <1.26.1	Fixed in 1.26.1
Go standard libraryos	Affected <1.25.8	Fixed in 1.25.8
Goos`pkg:golang/os`Other threats	Affected <1.25.8 >=1.26.0-0 <1.26.1	Fixed in 1.25.8 1.26.1

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

AI-suggested

Upgrade Go to a version later than 1.26.0-0 once patches addressing CVE-2026-27139 are released by the Go project.
If you cannot patch yet, avoid using File.ReadDir or File.Readdir in security-critical contexts where directory traversal or metadata leakage could be exploited.
Implement strict filesystem permissions and access controls to limit local user access to sensitive directories and files.
Use containerization or sandboxing to isolate processes and reduce the risk of local privilege escalation or information leakage.
Monitor and audit local user activities to detect unusual directory listing or metadata access patterns.
Consider application-level validation to ensure that file metadata accessed corresponds strictly to intended directories.
Educate developers about the risks of race conditions and encourage secure coding practices when handling filesystem operations.

Description

On Unix platforms, when listing the contents of a directory using File.ReadDir or File.Readdir the returned FileInfo could reference a file outside of the Root in which the File was opened. The impact of this escape is limited to reading metadata provided by lstat from arbitrary locations on the filesystem without permitting reading or writing files outside the root.

Impact

The primary impact of CVE-2026-27139 is limited confidentiality exposure of filesystem metadata outside the intended root directory. Although the vulnerability does not allow reading or modifying file contents, metadata such as file names, sizes, permissions, and timestamps can be leaked. This information disclosure could assist attackers in mapping the filesystem structure, identifying sensitive files, or planning further attacks. Since exploitation requires local access with low privileges and has high attack complexity, the risk is mitigated in environments with strict access controls. However, in multi-tenant or shared hosting environments where untrusted users have local access, this vulnerability could facilitate reconnaissance. The vulnerability does not affect integrity or availability, and no remote exploitation is possible. Overall, the impact is low but should not be ignored in sensitive or high-security environments.

CWE-363Race Condition Enabling Link Following (opens in a new tab)
Base weakness
The product checks the status of a file or directory before accessing it, which produces a race condition in which the file can be replaced with a link before the access is performed, causing the product to access the wrong file.
OWASP Cheat Sheets
Abuse Case (opens in a new tab)
OWASP ASVS 4.0.3
V1.11.2 (opens in a new tab)
V1.11.3 (opens in a new tab)
V11.1.6 (opens in a new tab)
Attack patterns
Leveraging Race Conditions (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 14 Mar 2026, 20:04 UTC

WeaknessesCWE-363

Technical details

References

Community reviews

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