Consul: Incorrect Regular Expression
CVE-2026-88021 is a high-severity incorrect regular expression vulnerability in Consul from HashiCorp, with a CVSS 3.1 base score of 7.1 out of 10. It can be exploited remotely over the network by an attacker with a low-privileged account, without any action from a user. The record lists version 2.0.4 as the first without the flaw, so updating Consul to that release or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 0.34% chance of exploitation within 30 days, which is low compared with other CVEs.
High severity with no evidence of exploitation so far.
What to do
- Update Consul to 2.0.4 or a later version.
- Update Consul Enterprise to 2.0.4 or a later version.
Affected products and versions
| Vendor | Product | Affected versions | Fixed in |
|---|---|---|---|
| HashiCorp | Consul | 1.9.0 up to, but not including, 2.0.4 | 2.0.4 |
| HashiCorp | Consul Enterprise | 1.9.0 up to, but not including, 2.0.4 | 2.0.4 |
Version data comes from the organisation that assigned the CVE. Confirm against the vendor advisory before deciding you are unaffected.
How the severity score breaks down
- Attack vector
- NetworkCan be exploited remotely over a network, including the internet.
- Attack complexity
- LowNo special conditions are needed; the attack works reliably.
- Privileges required
- LowA basic user account is enough.
- User interaction
- NoneNo action by a victim is required.
- Scope
- UnchangedImpact stays within the vulnerable component.
- Confidentiality
- HighAll data handled by the component can be read.
- Integrity
- LowLimited modification of data is possible.
- Availability
- NoneAvailability is not affected.
Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:H/I:L/A:N. Scored by CNA (hashicorp.com).
Official description
Consul and Consul Enterprise are vulnerable to an authorization bypass in the Connect service mesh that may allow a service to reach a destination it is not authorized to access. When building Envoy RBAC rules to enforce Connect intentions, Consul did not correctly escape certain characters in service names, namespaces, and partitions, causing the generated authorization rules to match more broadly than intended. This vulnerability (CVE-2026-88021) is fixed in Consul 2.0.4 and Consul Enterprise 1.21.18, 1.22.12 and 2.0.4.
Source: the CVE record as published by its numbering authority, via NVD and CVE.org.
The underlying weakness: Incorrect Regular Expression
The product specifies a regular expression in a way that causes data to be improperly matched or compared.
How developers prevent this class of flaw
- Regular expressions can become error prone when defining a complex language even for those experienced in writing grammars. Determine if several smaller regular expressions simplify one large regular expression. Also, subject the regular expression to thorough testing techniques such as equivalence partitioning, boundary value analysis, and robustness. After testing and a reasonable confidence level is achieved, a regular expression may not be foolproof. If an exploit is allowed to slip through, then record the exploit and refactor the regular expression.
Timeline
- CVE record published.
- CISA published its SSVC assessment (exploitation: none, automatable: no, technical impact: partial).
References
Other references
Other vulnerabilities in Consul
- 7.5 High severity
- 7.5 High severity
- 8.8 High severity
- 8.3 High severity
- 7.5 High severity
- 7.3 High severity
Recent Incorrect Regular Expression vulnerabilities
- 8.8 High severity
- 7.5 High severity
- 8.8 High severity
- 9.3 Critical severity
- 7.5 High severity
- 9.8 Critical severity
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