Critical SSRF

CVE-2026-55455 — Appsmith SSRF via Weak Outbound Host Filter in HTTP Datasources (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.

Published Jun 24, 2026 · Updated Oct 13, 2026 · Sources: NIST National Vulnerability Database, CVE Program (cve.org) e CISA ADP · CNA: GitHub_M

Low

Who exploits it and how urgent it is

A 0–100 score combining confirmed exploitation, ransomware and APT use, public exploits, EPSS and severity.

No exploitation signal in the sources consulted so far.

How the score was calculated

EPSS 0.4% (30-day exploitation probability)+5
Technical severity (critical)+10
CISA SSVC: exploitation "poc"+5

The score orders the patch queue; it does not replace your asset context (internet exposure, criticality, compensating controls).

Triage

Is it exploited, how likely is exploitation, what does it touch, and how severe do the sources call it.

Exploitation

Not confirmed

Not in CISA KEV — an absence of record, not proof it is unexploited.

EPSS FIRST

0.39%

ahead of 31% of scored CVEs · Oct 14, 2026

Affects

Appsmith

CVSS base

9.1

Critical · 3 source(s)

CISA SSVC assessment CISA

Three decision points CISA publishes for the CVEs it assesses (SSVC 2.0.3). A stakeholder decision, not a severity score.

Exploitation

Proof of concept

none · proof-of-concept · active

Automatable

can an attacker script the kill-chain steps

Technical impact

Partial

partial · total control of the vulnerable component

Remediation

Fixes and mitigations documented by the sources — linked to the original advisory.

No fix documented by the sources we poll. That does not mean none exists: check the vendor advisory.

First 24 hours

Ordered from the record’s own fields — exposure first, because you cannot patch what you have not found. A rule-generated starting point.

Identify exposed assets running the affected vendor/product/version combinations (Appsmith Appsmith, Appsmithorg Appsmith).
The attack is network-based and needs no privileges: restrict exposure (ACLs, VPN, WAF) until patched.
No fix documented in the sources: reduce exposure and monitor the vendor advisory.
Search available logs for exploit probes matching the vulnerability class (ssrf), errors and authentication anomalies.

Affected scope

Vendor, product and versions as the sources word them.

Vendor	Product	Versions	Status	Source
Appsmith	Appsmith	< 2.1	Vulnerable	NIST National Vulnerability Database
Appsmithorg	Appsmith	version < 2.1	Vulnerable	CVE Program (cve.org) e CISA ADP

Attack characteristics

The CVSS vector, decoded. It describes the attack, not your exposure to it.

Attack vector

Network

Attack complexity

Low

Privileges required

None

User interaction

None

Scope

Unchanged

Confidentiality

High

Integrity

High

Availability

None

Every base score collected

Sources score independently and may disagree; each row says who scored it and under which version.

Score	Version	Severity	Expl.	Impact	Scored by
5.3	CVSS 4.0	Medium	—	—	security-advisories@github.com via NIST National Vulnerability Database
5.3	CVSS 4.0	Medium	—	—	GitHub_M via CVE Program (cve.org) e CISA ADP
9.1	CVSS 3.1	Critical	3.9	5.2	nvd@nist.gov via NIST National Vulnerability Database

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:N (score shown at the top: nvd@nist.gov)

Weakness MITRE

Weakness class according to MITRE’s CWE catalog.

CWE-918 · Server-Side Request Forgery (SSRF)

Other CVEs with this weakness →

EPSS over time FIRST

Oct 13, 2026 → Oct 14, 2026 · 2 reading(s) · max 0.39%

Detection

Read off the CVSS vector and the weakness class. Starting points, not tested rules.

Prioritize edge telemetry for the network-reachable component (proxy, WAF, IDS/IPS).
Monitor outbound requests from the server to internal IPs and cloud metadata endpoints.

web/proxy/WAF logsnetwork IDS/IPSegress traffic

Analysis and videos

CVE-2026-55455: Appsmith SSRF via Weak Outbound Host Filter in HTTP Datasources
Appsmith versions before 2.1 contain a server-side request forgery (SSRF) weakness in the outbound host filter used by the REST API and GraphQL datasource plugins. The filter relies on an exact-match string denylist, so the broader address-class checks that exist on another code path (used by SMTP) are not applied to HTTP requests. The description states the issue is fixed in 2.1, and NVD lists a CVSS 3.1 base score of 9.1 (critical).

Timeline

What happened to this CVE, newest first.

2026
Affected products added · appsmithorg/appsmith
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
SSVC assessment updated
Oct 13, 2026 · CVE Program (cve.org) e CISA ADP
Record published
Oct 13, 2026
CVSS changed · 9.1
Oct 13, 2026 · NIST National Vulnerability Database
Source status changed · → Analyzed
Oct 13, 2026 · NIST National Vulnerability Database
Record created in this database
Oct 13, 2026 · NIST National Vulnerability Database
CVE published
Jun 24, 2026 · GitHub_M

Source activity

Repeated readings are counted rather than listed.

1× Official description updated · Oct 13, 2026 – Oct 13, 2026

References

1 on the record

github.com/appsmithorg/appsmith/security/advisories/GHSA-m23h-pvf3-2m7p
Third Party Advisory, x_refsource_CONFIRM, NIST National Vulnerability Database

Elsewhere on this site

Appsmith
every CVE for this vendor

SSRF
same class

CWE-918
other pages naming this weakness

Related CVEs (same products)

Critical CVE-2026-55454 Appsmith: Caddy admin API exposed without authentication Jun 24, 2026
Low CVE-2026-49979 Appsmith: SSRF via `POST /api/v1/admin/send-test-email` — JavaMail Bypasses WebClient IP Filter Jun 24, 2026
High CVE-2026-50189 Appsmith: RCE via Supervisord XML-RPC Admin Interface Exposed via /supervisor Caddy Route Jun 24, 2026
Medium CVE-2026-7299 CVE-2026-7299 Jun 2, 2026
High CVE-2026-5418 appsmithorg appsmith Dashboard WebClientUtils.java computeDisallowedHosts server-side request forgery Apr 2, 2026
Medium CVE-2026-34411 Appsmith < 1.98 Unauthenticated Instance Configuration Disclosure via Management APIs Mar 27, 2026

Not in any source we poll

Listed rather than left blank: an empty field and an unmeasured one look identical on screen, and only one is a reason to look elsewhere.

No fixed version, patch or mitigation documented.
No confirmed IOCs, IP addresses, domains, file hashes, or malware artifacts supplied.
No organization-specific asset inventory, compensating-control status, or patch deployment evidence supplied.
No exploit packet captures, log samples, or incident case IDs supplied.

Answered from this record

Text assembled only from the fields above — no additional claims.

What should defenders know first?

CVE-2026-55455 is "Appsmith SSRF via Weak Outbound Host Filter in HTTP Datasources (CVE-2026-55455)", rated Critical. It affects Appsmith (Appsmith); versions are in the scope table. It is not in CISA KEV, which does not rule out exploitation. CVSS 9.1 describes technical severity. EPSS 0.39% estimates the probability of exploitation in 30 days; neither replaces your asset context. First verify whether exposed or business-critical assets run the affected versions, apply vendor fixes or mitigations, and preserve logs for review.

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