CVE-2026-25479VulnerabilityPublished 9 Feb 2026

CVE-2026-25479: litestar · Incorrect Regular Expression

Affects litestarSource CVE Database V5

Not known to be exploited · CVSS 6.5 Medium : upgrade to 2.20.0 when convenient.

Data as of 26 Oct 2026, 06:26 UTC

CVSS 3.1 base score

6.5Medium

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

EPSS: 0.3% chance of exploitation in 30 days – higher than 29% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch: Available – fixed in 2.20.0

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

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

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: 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: 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 Feb 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 2026-10-26.

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 litestar to 2.20.0.

Affected software

Product	Affected	Fixed in
litestar-orglitestar	Affected <2.20.0	Fixed in 2.20.0

AI-suggested

The primary mitigation is to upgrade all litestar deployments to version 2.20.0 or later, where the vulnerability is fixed by escaping regex metacharacters in allowlist entries. Organizations should audit their current litestar versions and plan immediate upgrades. Additionally, review and sanitize all host allowlist configurations to ensure they do not contain unintended regex patterns or metacharacters. Implement strict input validation on Host headers at the application or web server level to reject suspicious or malformed hostnames. Employ web application firewalls (WAFs) with rules to detect and block anomalous Host header values. Conduct penetration testing focusing on host header injection and bypass scenarios to validate the effectiveness of mitigations. Finally, monitor logs for unusual host header patterns that could indicate exploitation attempts.

Description

CVE-2026-25479 is a medium-severity vulnerability in the litestar ASGI framework versions prior to 2.20.0. It arises from improper handling of allowlist host entries, where regex metacharacters are not escaped, allowing attackers to bypass intended hostname restrictions by supplying crafted host headers that match the regex but are not legitimate hosts. This can lead to partial confidentiality and integrity impacts without requiring authentication or user interaction. The vulnerability is fixed in litestar version 2.20.0. European organizations using vulnerable litestar versions in web applications may face risks of host header attacks, potentially enabling unauthorized access or manipulation of application behavior. Mitigation involves upgrading to version 2.

Impact

For European organizations, this vulnerability can undermine the security of web applications built on the litestar framework by allowing attackers to bypass host-based restrictions. This can lead to unauthorized access to application endpoints, potential leakage of sensitive information, or manipulation of application logic that depends on host validation. Industries with strict data protection requirements, such as finance, healthcare, and government, may face increased risk of confidentiality breaches. Additionally, attackers could exploit this flaw to perform web cache poisoning or redirect users to malicious sites, impacting user trust and compliance with regulations like GDPR. Since litestar is an ASGI framework often used in modern Python web applications, organizations using it in microservices or API gateways may see their internal network segmentation weakened. The medium severity indicates a moderate but non-trivial risk, especially if combined with other vulnerabilities or misconfigurations.

CWE-185Incorrect Regular Expression (opens in a new tab)
Class weakness
The product specifies a regular expression in a way that causes data to be improperly matched or compared.
Implementation · Refactoring
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.
Attack patterns
Command Delimiters (opens in a new tab)
Argument Injection (opens in a new tab)
Using Slashes in Alternate Encoding (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

Community reviews

Loading reviews…

Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 17 Feb 2026, 09:43 UTC

WeaknessesCWE-185

Technical details

References

Community reviews

Related threats