VulnerabilityPublished 13 Aug 2026Updated 10 Nov 2026

CVE-2026-123806: Sigstore · tuf has platform-dependent delegation path matching

Affects sigstoreSource GCVE Database

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Authoritative record:CVE-2026-123806· Medium 4.0

Not known to be exploited · CVSS 4.0 Medium : upgrade to 4.3.0 when convenient.

Data as of 10 Nov 2026, 18:55 UTC

CVSS 3.1 base score

4.0Medium

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

Thin evidence

One scorer or none

CVSS scores by source
CNA (GitHub_M)	CVSS 3.1	4.0

Patch: Available – fixed in 4.3.0

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

Attack Vector: Local
Attack Complexity: Low
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: None
Integrity: Low
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: 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: Low: Modification of data is possible, but the attacker does not have control over the consequence of a modification, or the amount of modification is limited. The data modification does not have a direct, serious impact on 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 9 Nov 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 10 Nov 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 sigstore to 4.3.0.

Affected software

Product	Affected	Fixed in
Homebrewsigstore`pkg:brew/sigstore`Other threats	Affected >=2.0.1 <4.3.0	Fixed in 4.3.0

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

AI-suggested

A patch is available in Sigstore version 4.3.0 that replaces fnmatch.fnmatch with fnmatch.fnmatchcase to ensure consistent, case-sensitive path pattern matching across platforms. Users should upgrade to version 4.3.0 or later to remediate this vulnerability. No other mitigation is required if the patch is applied.

Description

CVE-2026-123806 is a platform-dependent path pattern matching vulnerability in the python-tuf component of Sigstore. The issue arises because the delegation path matching uses Python's fnmatch.fnmatch, which applies case normalization differently on Windows (case-insensitive) versus POSIX systems (case-sensitive). This discrepancy can cause a TUF specification violation on Windows clients, allowing an attacker controlling a delegation role with a case-colliding path pattern to influence target authorization. The vulnerability affects Sigstore versions >=2.0.1 and <4.3.0 and is fixed in version 4.3.0.

Impact

On Windows clients, the vulnerability allows an attacker controlling a delegated role with a path pattern differing only in case from a legitimate delegation to cause the client to accept unauthorized targets by exploiting case-insensitive path matching. This violates the TUF specification and can lead to unauthorized target authorization. The impact is limited to Windows clients and requires specific repository configurations and attacker control of a delegation role. There is no impact on confidentiality or availability, only integrity is affected.

Summary

The vulnerability in Sigstore's python-tuf implementation stems from the use of fnmatch.fnmatch for delegation path pattern matching, which internally calls os.path.normcase. On POSIX systems, normcase is a no-op, preserving case sensitivity, but on Windows, normcase lowercases input and replaces slashes, making matching case-insensitive. This causes the authorization decision for target paths to differ by client OS, violating the TUF specification on Windows. An attacker controlling a delegated role with a path pattern differing only by case from a legitimate delegation can exploit this by having their delegation matched first on Windows clients, potentially causing the client to accept unauthorized targets. The fix replaces fnmatch.fnmatch with fnmatch.fnmatchcase, which does not apply case normalization and behaves consistently across platforms. The vulnerability requires a repository configured with case-colliding delegations, attacker control of one delegation, and a Windows client. It affects Sigstore versions from 2.0.1 up to but not including 4.3.0, with the fix in 4.3.0.

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Affected software

Description

AI analysisMachine-generated, updated 10 Nov 2026, 18:55 UTC

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