How severe is CVE-2026-55455?

CVE-2026-55455 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.

Is CVE-2026-55455 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (13th percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2026-55455?

CVE-2026-55455 affects Appsmith. See the affected-products list for the exact vulnerable versions.

How do I fix CVE-2026-55455?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.

Does CVE-2026-55455 have an EU (EUVD) identifier?

Yes. CVE-2026-55455 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-39111.

When was CVE-2026-55455 published?

CVE-2026-55455 was published on 2026-06-24 and last updated on 2026-06-26.

CVE-2026-55455

CVE-2026-55455 is a critical-severity vulnerability in Appsmith with a CVSS 3.x base score of 9.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-918.

Key facts

Severity: Critical (CVSS 3.x base score 9.1)
CVSS v4: 5.3
EPSS exploit prediction: 0% (13th percentile)
Actively exploited: Not listed in CISA KEV
EU (EUVD) id: EUVD-2026-39111
Weakness: CWE-918
Affected product: Appsmith
Published: 2026-06-24
Last modified: 2026-06-26

Description

Appsmith is a platform to build admin panels, internal tools, and dashboards. Prior to 2.1, the outbound HTTP host filter applied by WebClientUtils (used by the REST API and GraphQL datasource plugins) validates hosts against an exact-match string denylist. The comprehensive address-class check (loopback, any-local, link-local, fc00::/7) exists only on a separate code path used by SMTP, not by the HTTP plugin path. As a result, an authenticated user can craft outbound requests that reach loopback-bound services inside the container. This vulnerability is fixed in 2.1.

Frequently asked questions

What is CVE-2026-55455?: Appsmith is a platform to build admin panels, internal tools, and dashboards. Prior to 2.1, the outbound HTTP host filter applied by WebClientUtils (used by the REST API and GraphQL datasource plugins) validates hosts against an exact-match string denylist. The comprehensive address-class check (loopback, any-local, link-local, fc00::/7) exists only on a separate code path used by SMTP, not by the HTTP plugin path. As a result, an authenticated user can craft outbound requests that reach loopback-bound services inside the container. This vulnerability is fixed in 2.1.
How severe is CVE-2026-55455?: CVE-2026-55455 has a CVSS 3.x base score of 9.1, rated critical severity. It is exploitable over network with low attack complexity, requires no privileges and no user interaction. Impact on confidentiality is high, integrity high, and availability none.
Is CVE-2026-55455 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 0% (13th percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2026-55455?: CVE-2026-55455 affects Appsmith. See the affected-products list for the exact vulnerable versions.
How do I fix CVE-2026-55455?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround. Given its critical severity, prioritise patching exposed systems.
Does CVE-2026-55455 have an EU (EUVD) identifier?: Yes. CVE-2026-55455 is tracked in the ENISA EU Vulnerability Database (EUVD) as EUVD-2026-39111.
When was CVE-2026-55455 published?: CVE-2026-55455 was published on 2026-06-24 and last updated on 2026-06-26.

References

https://github.com/appsmithorg/appsmith/security/advisories/GHSA-m23h-pvf3-2m7p

Affected products (1)

cpe:2.3:a:appsmith:appsmith:*:*:*:*:*:*:*:*

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