VulnerabilityPublished 12 Jun 2026Updated 15 Jun 2026

CVE-2026-53607: apostrophecms apostrophe · Server-Side Request Forgery (SSRF)

Affects apostrophecms apostropheSource CVE Database V5

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Not known to be exploited · CVSS 3.7 Low.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score

3.7Low

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

EPSS: 0.2% chance of exploitation in 30 days – higher than 19% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.

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

Attack Vector: Network
Attack Complexity: High
Privileges Required: None
User Interaction: None
Scope: Unchanged
Confidentiality: Low
Integrity: None
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: High: A successful attack depends on conditions beyond the attacker's control. That is, a successful attack cannot be accomplished at will, but requires the attacker to invest in some measurable amount of effort in preparation or execution against the vulnerable component before a successful attack can be expected. For example, a successful attack may require an attacker to: gather knowledge about the environment in which the vulnerable target/component exists; prepare the target environment to improve exploit reliability; or inject themselves into the logical network path between the target and the resource requested by the victim in order to read and/or modify network communications (e.g., a man in the middle attack).
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: None: There is no loss of integrity within 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 12 Jun 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 30 Oct 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

Affected software

Product	Affected	Fixed in
apostrophecmsapostrophe	Affected <=4.30.0	Fixed in–

AI-suggested

Administrators should consider disabling the prettyUrls option in @apostrophecms/file or avoid using local uploadfs storage until a fix is released. Monitor the vendor advisory for updates. Since this vulnerability requires prettyUrls enabled and local storage, changing these configurations mitigates the risk. Avoid exposing the apostrophe server to untrusted networks where attackers can send arbitrary Host headers.

Description

### Summary When `prettyUrls: true` is enabled on `@apostrophecms/file` (a documented SEO feature for serving uploaded files at clean URLs), the public pretty-URL handler builds the upstream URL using the raw `Host` HTTP request header: ```js proxyUrl = `${req.protocol}://${req.get('host')}${uglyUrl}` ``` That URL is then `fetch`'ed and the response body + headers are streamed straight back to the requester. Because `Host` is fully attacker-controlled, an **unauthenticated remote** attacker can pivot the apostrophe process to issue outbound HTTP requests against any host it can reach on the private network. The path component is constrained to `/uploads/attachments/<cuid>-<slug>.<ext>` (built from a local-DB lookup), which keeps the impact narrow: cross-instance data exfiltration is neutralised by cuid uniqueness, but blind-SSRF residuals remain (network-topology mapping via response-code / timing differences and verbose proxy/WAF 404 body disclosure). Verified on `apostrophe@4.30.0` (latest); no fixed release exists. - **Affected:** `apostrophe <= 4.30.0` when `@apostrophecms/file` is configured with `prettyUrls: true` and uploadfs is **local** (the default; S3/CDN deployments produce an absolute `uglyUrl` and are not affected). ### Details `modules/@apostrophecms/file/index.js` (excerpt; the public GET route registered when `prettyUrls: true`): ```js if (!self.options.prettyUrls) return; return { get: { async [`${self.options.prettyUrlDir}/*`](req, res) { const matches = (req.params[0] || '').match(/^([^.]+)\.\w+$/); if (!matches) return res.status(400).send('invalid'); const [ , slug ] = matches; if (slug.includes('..') || slug.includes('/')) { return res.status(403).send('forbidden'); } const file = await self.find(req, { slug: `${self.options.slugPrefix}${slug}` }).toObject(); if (!file) return res.status(404).send('not found'); const uglyUrl = self.apos.attachment.url(file.attachment, { prettyUrl: false }); const proxyUrl = uglyUrl.startsWith('/') ? `${req.protocol}://${req.get('host')}${uglyUrl}` // <-- sink : uglyUrl; return await streamProxy(req, proxyUrl, { error: self.apos.util.error }); } } }; ``` `lib/stream-proxy.js` (excerpt): ```js module.exports = async function(req, url, { error }) { const res = req.res; if (url.startsWith('/')) url = `${req.baseUrl}${url}`; let response; try { response = await fetch(url); } // <-- attacker-steered fetch catch (e) { return send502(e); } for (const header of ['content-type','etag','last-modified','content-disposition','cache-control']) { const v = response.headers.get(header); if (v != null) res.header(header, v); } res.status(response.status); response.body.pipeTo(new WritableStream({ write(c){ res.write(c) }, close(){ res.end() }, ... })); }; ``` `req.get('host')` returns the unvalidated `Host` HTTP header from the request. Express does not validate or restrict it, and apostrophe does not check the constructed `proxyUrl` against an allowlist. The upstream's body and content-type are forwarded verbatim — so any response the targeted host does return at the constrained path will reach the attacker. In practice the path constraint (`/uploads/attachments/<cuid>-<slug>.<ext>`) and cuid uniqueness mean meaningful body exfiltration only occurs against verbose-404 / banner- leaky proxies; against most internal services this degenerates to blind SSRF (response-code + timing side channels). Prerequisites are minimal: `prettyUrls: true` (a documented production SEO option) + at least one file uploaded with a known slug. Slugs are publicly enumerable in normal CMS use (file URLs appear in page content). **Distinct from the only published apostrophe SSRF advisory, GHSA-pr28-mf3q-qpg6** ("Authenticated SSRF in rich-text widget import via @apostrophecms/area validate-widget"), which is authenticated and lives in a completely different module/route. This finding is unauthenticated, in `@apostrophecms/file`, via the `Host` header. ### PoC Three services on an isolated Docker network: `mongo`, `internal` (returns a fake secret, **never exposed to the host**), `apos:3000` (the only port the host can reach). The host attacker proves it cannot reach `internal` directly, then exfiltrates `internal`'s response via one crafted request to `apos`. `app.js` (normal apostrophe site, documented option only): ```js require('apostrophe')({ shortName: 'apos-ssrf-poc', autoBuild: false, modules: { '@apostrophecms/express': { options: { session: { secret: 'x' }, port: 3000 } }, '@apostrophecms/db': { options: { uri: process.env.APOS_MONGODB_URI } }, '@apostrophecms/asset': { options: { autoBuild: false, publicBundle: false, watch: false, hmr: false } }, '@apostrophecms/file': { options: { prettyUrls: true, prettyUrlDir: '/files' } }, 'poc-seed': {} // seeds one file doc on boot (= what an admin does

Impact

An unauthenticated remote attacker can exploit this SSRF vulnerability to make the apostrophe server issue HTTP requests to internal network hosts reachable by the server. Although the path is constrained and limits direct data exfiltration, attackers can perform network topology mapping and blind SSRF attacks using response timing and status codes. The impact is limited to information disclosure and reconnaissance; no direct code execution or data modification is indicated. The CVSS score is 3.7 (low) reflecting limited confidentiality impact and high attack complexity.

Summary

The vulnerability (CVE-2026-53607) arises from the public pretty-URL handler in @apostrophecms/file when prettyUrls is enabled. The handler constructs an upstream URL using the raw Host HTTP header from the request without validation, then fetches the resource and streams the response back to the client. Since the Host header is attacker-controlled, an unauthenticated attacker can induce the server to make HTTP requests to internal network hosts at paths constrained to /uploads/attachments/<cuid>-<slug>.<ext>. The uniqueness of cuid limits meaningful data exfiltration, but blind SSRF remains possible through response codes and timing. This affects apostrophe versions up to 4.30.0 with local uploadfs; S3/CDN deployments are not affected. No fixed version or patch is currently available.

CWE-918Server-Side Request Forgery (opens in a new tab)
Base weaknessCWE Top 25 (2025): #22OWASP Top 10 A01:2025: Broken Access Control (opens in a new tab)
The web server receives a URL or similar request from an upstream component and retrieves the contents of this URL, but it does not sufficiently ensure that the request is being sent to the expected destination.
Implementation · Operation
If there is a known list of applications, IP, hostname, and/or domains to which the product is allowed to communicate, then use allowlists to ensure that outgoing requests are restricted to these known entities. The allowlists could be in the application code or possibly enforced by firewalls or network segmentation.
Implementation · Operation
If the product is expected to be able to connect to arbitrary IP addresses or domains, consider using a denylist that includes private network addresses, internal domain names, etc. The denylist could be in the application code or possibly enforced by firewalls or network segmentation.
Implementation · Input Validation
Assume all input is malicious. Use an "accept known good" input validation strategy, i.e., use a list of acceptable inputs that strictly conform to specifications. Reject any input that does not strictly conform to specifications, or transform it into something that does.
OWASP Cheat Sheets
Server Side Request Forgery Prevention (opens in a new tab)
Unvalidated Redirects and Forwards (opens in a new tab)
Cross Site Scripting Prevention (opens in a new tab)
DOM based XSS Prevention (opens in a new tab)
Authorization (opens in a new tab)
OWASP ASVS 4.0.3
V12.6.1 (opens in a new tab)
V5.2.6 (opens in a new tab)
Attack patterns
Server Side Request Forgery (opens in a new tab)
From MITRE CWE, MITRE CAPEC and OWASP (Top 10, OpenCRE).

References

github.com/apostrophecms/apostrophe/security/advisories/GHSA-34pj-2622-jvxq (opens in a new tab)

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Exploitation evidence

What to do

Affected software

Description

AI analysisMachine-generated, updated 1 Aug 2026, 21:29 UTC

WeaknessesCWE-918

Technical details

References

Community reviews

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