CVE-2026-23831VulnerabilityPublished 22 Jan 2026

CVE-2026-23831: sigstore rekor · NULL Pointer Dereference

Affects sigstore rekorSource CVE Database V5

Not known to be exploited · CVSS 5.3 Medium : upgrade to 1.5.0 when convenient.

Data as of 25 Oct 2026, 19:02 UTC

CVSS 3.1 base score

5.3Medium

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

EPSS: 0.4% chance of exploitation in 30 days – higher than 36% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 1.5.0

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

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

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: None: There is no loss of confidentiality within the impacted component.
Integrity: None: There is no loss of integrity within the impacted component.
Availability: Low: Performance is reduced or there are interruptions in resource availability. Even if repeated exploitation of the vulnerability is possible, the attacker does not have the ability to completely deny service to legitimate users. The resources in the impacted component are either partially available all of the time, or fully available only some of the time, but overall there is no direct, serious consequence to the impacted component.

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 rekor and github.com/sigstore/rekor to 1.5.0.

Affected software

Product	Affected	Fixed in
sigstorerekor	Affected <1.5.0	Fixed in 1.5.0
Gogithub.com/sigstore/rekor`pkg:golang/github.com/sigstore/rekor`Other threats	Affected <1.5.0	Fixed in 1.5.0

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

AI-suggested

1. Upgrade all instances of sigstore Rekor to version 1.5.0 or later, where the vulnerability is fixed. 2. Implement strict input validation on proposed entries before processing to ensure spec.message is not empty or malformed, preventing triggering of the NULL pointer dereference. 3. Monitor Rekor service logs and metrics for increased 500 Internal Server Error responses, which may indicate exploitation attempts or malformed inputs. 4. Employ rate limiting or request filtering on the Rekor API endpoints to reduce the risk of denial of service through repeated malformed requests. 5. Integrate automated alerting for anomalous thread panics or service errors to enable rapid incident response. 6. Review and test CI/CD pipelines to ensure resilience against transient Rekor service disruptions. 7. Consider deploying Rekor instances in high-availability configurations to mitigate impact of single-thread failures. 8. Educate development and security teams about the importance of keeping supply chain tooling up to date and monitoring for vulnerabilities.

Description

CVE-2026-23831 is a medium severity vulnerability in sigstore's Rekor component (versions prior to 1.5.0) involving a NULL pointer dereference triggered by attacker-controlled input. Specifically, when a proposed entry with an empty spec.message is processed, the validate() function incorrectly returns success without initializing sign1Msg, leading to a panic in Canonicalize() when it dereferences the uninitialized pointer. This causes a thread panic resulting in a 500 error response to clients but does not crash the entire service, thus limiting availability impact. No confidentiality or integrity impact is observed. The vulnerability requires no authentication or user interaction and can be triggered remotely via crafted input. The issue has been fixed in version 1.5.

Impact

For European organizations, the primary impact of CVE-2026-23831 is a potential denial of service condition affecting the availability of the Rekor transparency log service. Since Rekor is used to provide tamper-evident logging for software supply chains, any disruption could delay or interrupt automated verification of software artifacts, impacting continuous integration/continuous deployment (CI/CD) workflows and supply chain security assurances. Although the vulnerability does not compromise confidentiality or integrity, availability interruptions could reduce trust in the supply chain verification process and cause operational delays. Organizations relying heavily on sigstore Rekor for software provenance, especially in critical infrastructure, financial services, or government sectors, may experience workflow disruptions. The limited scope of the denial of service (single thread panic with recovery) means the overall service remains up, but repeated exploitation could degrade performance or cause intermittent failures. European entities with mature DevSecOps practices and cloud-native environments are more likely to be affected due to higher adoption of sigstore tools.

CWE-476NULL Pointer Dereference (opens in a new tab)
Base weaknessLikelihood of exploit: MediumCWE Top 25 (2025): #13OWASP Top 10 A10:2025: Mishandling of Exceptional Conditions (opens in a new tab)
The product dereferences a pointer that it expects to be valid but is NULL.
Implementation
For any pointers that could have been modified or provided from a function that can return NULL, check the pointer for NULL before use. When working with a multithreaded or otherwise asynchronous environment, ensure that proper locking APIs are used to lock before the check, and unlock when it has finished.
Requirements
Select a programming language that is not susceptible to these issues.
Implementation
Check the results of all functions that return a value and verify that the value is non-null before acting upon it.
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

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 30 Jan 2026, 10:18 UTC

WeaknessesCWE-476

Technical details

References

Community reviews

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