How severe is CVE-2026-27018?

No CVSS score has been assigned to CVE-2026-27018 yet. Review the advisory details and affected package list to assess your exposure.

Which packages are affected by CVE-2026-27018?

CVE-2026-27018 affects the following packages: github.com/gotenberg/gotenberg/v8 (Go), github.com/gotenberg/gotenberg/v7 (Go). Ecosystems affected: Go.

How do I fix CVE-2026-27018?

Update github.com/gotenberg/gotenberg/v8 to 8.29.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-27018 is resolved across your whole dependency graph.

How do I detect CVE-2026-27018 in my Go dependencies?

Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/gotenberg/gotenberg/v8, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

How do I mitigate CVE-2026-27018 if there is no patch (or I can't update yet)?

If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.

How does O3 Security protect against CVE-2026-27018?

O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-27018 can be triaged on real exposure rather than presence alone.

Is CVE-2026-27018 actively exploited in the wild?

No public exploit code has been indexed for CVE-2026-27018 yet. This does not mean the vulnerability cannot be exploited — absence of public exploits does not imply safety. Apply the recommended fix and use O3 Security to monitor your exposure.

What is the EPSS score for CVE-2026-27018?

CVE-2026-27018 has an EPSS (Exploit Prediction Scoring System) score of 1.7%, placing it in the 76th percentile of all CVEs. EPSS is maintained by FIRST.org and estimates the probability that a vulnerability will be exploited in the wild within the next 30 days. This score indicates relatively lower exploitation probability, though the CVSS severity should still guide your patching priority.

What type of vulnerability is CVE-2026-27018?

CVE-2026-27018 is classified as Path Traversal (CWE-22), Server-Side Request Forgery (SSRF) (CWE-918). These weakness types describe the underlying flaw category, which helps determine the potential impact and the right class of mitigation. This is a high-impact weakness class that often enables remote code execution or data exposure.

When was CVE-2026-27018 published, and has it been updated?

CVE-2026-27018 was published on March 30, 2026 and was last updated on August 12, 2026. Advisory data evolves as severity scores, affected ranges, and exploit intelligence are revised — always check the latest version of the advisory before acting.

🐹 Go

Not in CISA KEV

CVE-2026-27018 — v8

Fix: gotenberg/gotenberg@06b2b2e

CVE-2026-27018 is a Path Traversal vulnerability in github.com/gotenberg/gotenberg/v8. A fix is available for github.com/gotenberg/gotenberg/v8 — see the affected versions and patch details below.

Gotenberg: Chromium deny-list bypass via case-insensitive URL scheme

Also known asGHSA-jjwv-57xh-xr6rGO-2026-4905

Published

Mar 30, 2026

Updated

Aug 12, 2026

Affected

2 pkgs

Patched

1 / 2

Exploits

None indexed

Exploitation data as of Sep 21, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

Exploitation Status

Proof-of-concept exploit code exists

CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
CISA assesses this as automatable — exploitation doesn’t require manual, per-target effort, which raises the odds of mass scanning and opportunistic attacks.

Exploitation and automatability from CISA’s SSVC triage for CVE-2026-27018.

EPSS Exploitation Probability

via FIRST.org ↗

1.7%probability of exploitation in next 30 days

Lower Risk0.00%

Lower risk than most CVEs76th percentile — riskier than 76% of all scored CVEsHighest risk

EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.

Real-World Exposure

2 pkgs affected

🐹github.com/gotenberg/gotenberg/v8🐹github.com/gotenberg/gotenberg/v7

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Go packages — download data is not available via public APIs for these ecosystems.

Description

Impact

The fix introduced in version 8.1.0 for GHSA-rh2x-ccvw-q7r3 (CVE-2024-21527) can be bypassed using mixed-case or uppercase URL schemes.

The default --chromium-deny-list value is ^file:(?!//\/tmp/).*. This regex is anchored to lowercase file: at the start. However, per RFC 3986 Section 3.1, URI schemes are case-insensitive. Chromium normalizes the scheme to lowercase before navigation, so a URL like FILE:///etc/passwd or File:///etc/passwd bypasses the deny-list check but still gets resolved by Chromium as file:///etc/passwd.

The root cause is in pkg/gotenberg/filter.go — the FilterDeadline function compiles the deny-list regex with regexp2.MustCompile(denied.String(), 0), where 0 means no flags (case-sensitive). Since the regex pattern itself doesn't include a (?i) flag, matching is strictly case-sensitive.

This affects both the URL endpoint and HTML conversion (via iframes, link tags, etc.).

Steps to Reproduce

Start Gotenberg with default settings:

docker run --rm -p 3000:3000 gotenberg/gotenberg:8.26.0 gotenberg

Read /etc/passwd via the URL endpoint using an uppercase scheme:

curl -X POST 'http://localhost:3000/forms/chromium/convert/url' \
  --form 'url=FILE:///etc/passwd' -o output.pdf

Open output.pdf — it contains the contents of /etc/passwd.
Alternatively, create an index.html:

<iframe src="FILE:///etc/passwd" width="100%" height="100%"></iframe>

Then convert it:

curl -X POST 'http://localhost:3000/forms/chromium/convert/html' \
  -F '[email protected]' -o output.pdf

The resulting PDF contains /etc/passwd contents.

Mixed-case variants like File:, fILE:, fiLE: etc. all work as well.

Root Cause

pkg/modules/chromium/chromium.go defines the default deny-list as ^file:(?!//\/tmp/).*
pkg/gotenberg/filter.go compiles this with regexp2.MustCompile(denied.String(), 0) — flag 0 means case-sensitive
pkg/modules/chromium/events.go uses FilterDeadline to check intercepted request URLs against the deny-list
Chromium normalizes URL schemes to lowercase, so FILE:///etc/passwd becomes file:///etc/passwd after the deny-list check has already passed

Suggested Fix

Change the default deny-list regex to use a case-insensitive flag:

(?i)^file:(?!//\/tmp/).*

Or apply case-insensitive matching in FilterDeadline when compiling the regex.

Severity

This is effectively the same impact as CVE-2024-21527 — unauthenticated arbitrary file read from the Gotenberg container. An attacker can leak environment variables, configuration, credentials, and other sensitive data.

Affected Packages

2 total 1 fixed

Ecosystem	Package	Vulnerable range	Fix
🐹Go	`github.com/gotenberg/gotenberg/v8`	all versions	8.29.0`go get github.com/gotenberg/gotenberg/v8@v8.29.0`
🐹Go	`github.com/gotenberg/gotenberg/v7`	all versions	No fix

Detection & mitigation playbook

Open-source dependency

Detect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/gotenberg/gotenberg/v8, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/gotenberg/gotenberg/v8 to 8.29.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2026-27018 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2026-27018 can be triaged on real exposure rather than presence alone.

Tailored to CVE-2026-27018. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.

Frequently Asked Questions

### Impact The fix introduced in version 8.1.0 for GHSA-rh2x-ccvw-q7r3 (CVE-2024-21527) can be bypassed using mixed-case or uppercase URL schemes. The default `--chromium-deny-list` value is `^file:(?!//\/tmp/).*`. This regex is anchored to lowercase `file:` at the start. However, per RFC 3986 Section 3.1, URI schemes are case-insensitive. Chromium normalizes the scheme to lowercase before navigation, so a URL like `FILE:///etc/passwd` or `File:///etc/passwd` bypasses the deny-list check but still gets resolved by Chromium as `file:///etc/passwd`. The root cause is in `pkg/gotenberg/filter.

O3 Security · Impact-Aware SCA

Is CVE-2026-27018 in your dependencies?

O3 Security finds CVE-2026-27018 across Go dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.

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