CVE-2026-23991VulnerabilityPublished 22 Jan 2026

CVE-2026-23991: theupdateframework go-tuf · Reachable Assertion

Affects theupdateframework go-tufSource CVE Database V5

Not known to be exploited · CVSS 5.9 Medium : upgrade to 2.3.1 when convenient.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

5.9Medium

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

EPSS: 0.5% chance of exploitation in 30 days – higher than 47% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.3.1

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

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

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: 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: 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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: High: There is total loss of availability, resulting in the attacker being able to fully deny access to resources in the impacted component; this loss is either sustained (while the attacker continues to deliver the attack) or persistent (the condition persists even after the attack has completed). Alternatively, the attacker has the ability to deny some availability, but the loss of availability presents a direct, serious consequence to the impacted component (e.g., the attacker cannot disrupt existing connections, but can prevent new connections; the attacker can repeatedly exploit a vulnerability that, in each instance of a successful attack, leaks a only small amount of memory, but after repeated exploitation causes a service to become completely unavailable).

Definitions: FIRST CVSS v3.1 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 22 Jan 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 2026-10-25.

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-tuf and github.com/theupdateframework/go-tuf to 2.3.1.

Affected software

Product	Affected	Fixed in
theupdateframeworkgo-tuf	Affected >=2.0.0 <2.3.1	Fixed in 2.3.1
Gogithub.com/theupdateframework/go-tuf`pkg:golang/github.com/theupdateframework/go-tuf`Other threats	Affected >=2.0.0 <2.3.1	Fixed in 2.3.1

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

AI-suggested

The definitive mitigation for CVE-2026-23991 is to upgrade all go-tuf client implementations to version 2.3.1 or later, where the parsing logic has been corrected to prevent panics on malformed metadata. Organizations should audit their software supply chain components to identify usage of affected go-tuf versions and prioritize patching. Implementing network-level protections to restrict access to trusted TUF repositories and mirrors can reduce exposure to malicious metadata injections. Monitoring and alerting on unexpected client crashes or update failures can help detect exploitation attempts. Where feasible, deploying redundancy in update mirrors and validating metadata integrity through additional layers can provide resilience. Security teams should also review incident response plans to address potential DoS scenarios in update infrastructure. Finally, engaging with software vendors and upstream maintainers to ensure timely updates and vulnerability disclosures is recommended.

Description

CVE-2026-23991 is a medium severity vulnerability in go-tuf, a Go implementation of The Update Framework (TUF). Versions from 2.0.0 up to but not including 2.3.1 are affected. The vulnerability arises when the TUF repository or its mirrors return invalid but syntactically correct JSON metadata that is not well-formed according to TUF specifications. This causes the client to panic during parsing before signature validation, resulting in a denial of service (DoS). An attacker controlling a repository, mirror, or cache can exploit this without needing signing keys. No user interaction or authentication is required, and no known workarounds exist.

Impact

For European organizations, the primary impact of CVE-2026-23991 is the potential for denial of service in software update processes that rely on go-tuf. This can disrupt automated update mechanisms, delaying critical patches and exposing systems to other vulnerabilities. Organizations using go-tuf in production environments, especially those managing large-scale software deployments or cloud services, may experience service outages or degraded reliability. The inability to validate updates properly could erode trust in the update infrastructure and complicate incident response. Although no direct compromise of confidentiality or integrity occurs, the availability impact can indirectly increase risk exposure. Sectors such as finance, healthcare, telecommunications, and government, which depend heavily on timely and secure software updates, are particularly vulnerable. Additionally, supply chain attacks could leverage this vulnerability to cause widespread disruption by targeting update repositories or mirrors. The lack of known exploits reduces immediate risk but does not eliminate the threat, especially given the ease of exploitation without authentication or user interaction.

CWE-617Reachable Assertion (opens in a new tab)
Base weakness
The product contains an assert() or similar statement that can be triggered by an attacker, which leads to an application exit or other behavior that is more severe than necessary.
Implementation
Make sensitive open/close operation non reachable by directly user-controlled data (e.g. open/close resources)
Implementation · Input Validation
Perform input validation on user data.
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).
CWE-754Improper Check for Unusual or Exceptional Conditions (opens in a new tab)
Class weaknessLikelihood of exploit: MediumOWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product does not check or incorrectly checks for unusual or exceptional conditions that are not expected to occur frequently during day to day operation of the product.
Requirements · Language Selection
Use a language that does not allow this weakness to occur or provides constructs that make this weakness easier to avoid.
Implementation
Check the results of all functions that return a value and verify that the value is expected.
Implementation
If using exception handling, catch and throw specific exceptions instead of overly-general exceptions (CWE-396, CWE-397). Catch and handle exceptions as locally as possible so that exceptions do not propagate too far up the call stack (CWE-705). Avoid unchecked or uncaught exceptions where feasible (CWE-248).
OWASP Cheat Sheets
Logging (opens in a new tab)
Error Handling (opens in a new tab)
OWASP ASVS 4.0.3
V11.1.7 (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 29 Jan 2026, 08:50 UTC

WeaknessesCWE-617, CWE-754

Technical details

References

Community reviews

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