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CVE-2026-42596

Gotenberg: Unauthenticated SSRF via default deny-list bypass in downloadFrom and webhook

9.4 CriticalFix available

Gotenberg is a Docker-powered stateless API for PDF files. Prior to 8.31.0, the default deny-lists used by Gotenberg's downloadFrom feature and webhook feature are bypassable. Because the filter is regex-based and case-sensitive, an unauthenticated attacker can supply URLs such as http://[::ffff:127.0.0.1]:... and reach loopback or private HTTP services that the default deny-list is intended to block. This crosses a real security boundary because an external caller can force the server to make outbound requests to internal-only targets. This vulnerability is fixed in 8.31.0.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
High
Integrity
High
Availability
Low

Exploit likelihood

1.59%Up 1.5 points since May 15, 2026
90%50%10%1%

What each source reports

CVE List Score used 9.4

Gotenberg: Unauthenticated SSRF via default deny-list bypass in downloadFrom and webhook

Gotenberg is a Docker-powered stateless API for PDF files. Prior to 8.31.0, the default deny-lists used by Gotenberg's downloadFrom feature and webhook feature are bypassable. Because the filter is regex-based and case-sensitive, an unauthenticated attacker can supply URLs such as http://[::ffff:127.0.0.1]:... and reach loopback or private HTTP services that the default deny-list is intended to block. This crosses a real security boundary because an external caller can force the server to make outbound requests to internal-only targets. This vulnerability is fixed in 8.31.0.

Record
CVE-2026-42596
CVSS 3.1
9.4 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Weakness
CWE-918
Updated
2026-11-02
EUVDEUVD-2026-30310 9.4

Gotenberg is a Docker-powered stateless API for PDF files. Prior to 8.31.0, the default deny-lists used by Gotenberg's downloadFrom feature and webhook feature are bypassable. Because the filter is regex-based and case-sensitive, an unauthenticated attacker can supply URLs such as http://[::ffff:127.0.0.1]:... and reach loopback or private HTTP services that the default deny-list is intended to block. This crosses a real security boundary because an external caller can force the server to make outbound requests to internal-only targets. This vulnerability is fixed in 8.31.0.

Record
EUVD-2026-30310
CVSS 3.1
9.4 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Updated
2026-11-02
GitHub AdvisoriesGHSA-4vmc-gm8v-m35h 9.4

Gotenberg vulnerable to unauthenticated SSRF via default deny-list bypass in downloadFrom and webhook

Summary

The default deny-lists used by Gotenberg's downloadFrom feature and webhook feature are bypassable. Because the filter is regex-based and case-sensitive, an unauthenticated attacker can supply URLs such as http://[::ffff:127.0.0.1]:... and reach loopback or private HTTP services that the default deny-list is intended to block. This crosses a real security boundary because an external caller can force the server to make outbound requests to internal-only targets.

Details

The issue originates from the shipped default deny-list regexes and the way those regexes are applied:

  • pkg/modules/api/api.go:198-200 defines the default api-download-from-deny-list.
  • pkg/modules/webhook/webhook.go:41-43 defines the default webhook-deny-list.
  • pkg/gotenberg/filter.go:20-69 evaluates those patterns with regexp2 using case-sensitive matching.

The attacker-controlled URL then reaches outbound request sinks:

  • pkg/modules/api/context.go:208-282
    • Reads attacker-supplied downloadFrom.
    • Calls gotenberg.FilterDeadline(...).
    • Issues an outbound GET with retryablehttp.NewRequest(...) and client.Do(...).
  • pkg/modules/webhook/middleware.go:99-217
    • Reads Gotenberg-Webhook-Url and Gotenberg-Webhook-Events-Url.
    • Calls gotenberg.FilterDeadline(...).
    • Constructs a client for outbound delivery.
  • pkg/modules/webhook/client.go:39-152
    • Sends the success or error webhook request.
  • pkg/modules/webhook/client.go:155-216
    • Sends the webhook event request.

Why the bypass works:

  1. The default deny-list only blocks lowercase http:// and https:// prefixes.
  2. The filtering logic performs case-sensitive regex matching on the raw user input.
  3. Go's HTTP stack accepts multiple textual representations of loopback/private addresses that are not covered by the default regex, including IPv4-mapped IPv6 loopback like http://[::ffff:127.0.0.1]:18081/....
  4. As a result, a URL can fail the deny-list check but still be interpreted as a valid loopback/private destination by the outbound client.

Confirmed bypass used during verification:

  • http://[::ffff:127.0.0.1]:18081/page_1.pdf
  • http://[::ffff:127.0.0.1]:18082/upload
  • http://[::ffff:127.0.0.1]:18082/events

This is not the same issue as the previously published Chromium deny-list advisories. This finding affects the separate downloadFrom and webhook URL filtering paths.

PoC

One-command verification

From the repository root:

cd '/Users/r1zzg0d/Documents/CVE hunting/targets/gotenberg'
./tmp/poc/verify_ssrf_poc.sh

What the script does:

  1. Builds or reuses a slim local Gotenberg image that contains only the modules needed for this proof.
  2. Starts Gotenberg on 127.0.0.1:3000.
  3. Starts an internal-only helper listener inside the same container network namespace.
  4. Verifies downloadFrom SSRF by forcing Gotenberg to fetch a PDF from http://[::ffff:127.0.0.1]:18081/page_1.pdf.
  5. Verifies webhook SSRF by forcing Gotenberg to POST to http://[::ffff:127.0.0.1]:18082/upload and http://[::ffff:127.0.0.1]:18082/events.
  6. Writes evidence artifacts to disk.

Expected success output:

[4/6] Verifying downloadFrom SSRF bypass with http://[::ffff:127.0.0.1]:18081/page_1.pdf
PASS downloadFrom: Gotenberg fetched an internal-only loopback URL and returned PDF metadata
[5/6] Verifying webhook SSRF bypass with http://[::ffff:127.0.0.1]:18082/upload
PASS webhook: Gotenberg POSTed to an internal-only loopback listener

Evidence files created by the script:

  • /Users/r1zzg0d/Documents/CVE hunting/targets/gotenberg/tmp/poc/artifacts/downloadfrom-metadata.json
  • /Users/r1zzg0d/Documents/CVE hunting/targets/gotenberg/tmp/poc/artifacts/webhook.log

Manual evidence commands

The following commands were run after the verifier completed successfully:

jq '.' '/Users/r1zzg0d/Documents/CVE hunting/targets/gotenberg/tmp/poc/artifacts/downloadfrom-metadata.json'
cat…
Record
GHSA-4vmc-gm8v-m35h
CVSS 3.1
9.4 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Weakness
CWE-918
Updated
2026-11-02
NVD 9.4

Gotenberg is a Docker-powered stateless API for PDF files. Prior to 8.31.0, the default deny-lists used by Gotenberg's downloadFrom feature and webhook feature are bypassable. Because the filter is regex-based and case-sensitive, an unauthenticated attacker can supply URLs such as http://[::ffff:127.0.0.1]:... and reach loopback or private HTTP services that the default deny-list is intended to block. This crosses a real security boundary because an external caller can force the server to make outbound requests to internal-only targets. This vulnerability is fixed in 8.31.0.

Record
CVE-2026-42596
CVSS 3.1
9.4 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Weakness
CWE-918
Updated
2026-11-02
OSV 9.4

Gotenberg: Unauthenticated SSRF via default deny-list bypass in downloadFrom and webhook

Gotenberg is a Docker-powered stateless API for PDF files. Prior to 8.31.0, the default deny-lists used by Gotenberg's downloadFrom feature and webhook feature are bypassable. Because the filter is regex-based and case-sensitive, an unauthenticated attacker can supply URLs such as http://[::ffff:127.0.0.1]:... and reach loopback or private HTTP services that the default deny-list is intended to block. This crosses a real security boundary because an external caller can force the server to make outbound requests to internal-only targets. This vulnerability is fixed in 8.31.0.

Record
CVE-2026-42596
CVSS 3.1
9.4 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Weakness
CWE-918
Updated
2026-11-02
OSVGHSA-4vmc-gm8v-m35h 9.4

Gotenberg vulnerable to unauthenticated SSRF via default deny-list bypass in downloadFrom and webhook

Summary

The default deny-lists used by Gotenberg's downloadFrom feature and webhook feature are bypassable. Because the filter is regex-based and case-sensitive, an unauthenticated attacker can supply URLs such as http://[::ffff:127.0.0.1]:... and reach loopback or private HTTP services that the default deny-list is intended to block. This crosses a real security boundary because an external caller can force the server to make outbound requests to internal-only targets.

Details

The issue originates from the shipped default deny-list regexes and the way those regexes are applied:

  • pkg/modules/api/api.go:198-200 defines the default api-download-from-deny-list.
  • pkg/modules/webhook/webhook.go:41-43 defines the default webhook-deny-list.
  • pkg/gotenberg/filter.go:20-69 evaluates those patterns with regexp2 using case-sensitive matching.

The attacker-controlled URL then reaches outbound request sinks:

  • pkg/modules/api/context.go:208-282
    • Reads attacker-supplied downloadFrom.
    • Calls gotenberg.FilterDeadline(...).
    • Issues an outbound GET with retryablehttp.NewRequest(...) and client.Do(...).
  • pkg/modules/webhook/middleware.go:99-217
    • Reads Gotenberg-Webhook-Url and Gotenberg-Webhook-Events-Url.
    • Calls gotenberg.FilterDeadline(...).
    • Constructs a client for outbound delivery.
  • pkg/modules/webhook/client.go:39-152
    • Sends the success or error webhook request.
  • pkg/modules/webhook/client.go:155-216
    • Sends the webhook event request.

Why the bypass works:

  1. The default deny-list only blocks lowercase http:// and https:// prefixes.
  2. The filtering logic performs case-sensitive regex matching on the raw user input.
  3. Go's HTTP stack accepts multiple textual representations of loopback/private addresses that are not covered by the default regex, including IPv4-mapped IPv6 loopback like http://[::ffff:127.0.0.1]:18081/....
  4. As a result, a URL can fail the deny-list check but still be interpreted as a valid loopback/private destination by the outbound client.

Confirmed bypass used during verification:

  • http://[::ffff:127.0.0.1]:18081/page_1.pdf
  • http://[::ffff:127.0.0.1]:18082/upload
  • http://[::ffff:127.0.0.1]:18082/events

This is not the same issue as the previously published Chromium deny-list advisories. This finding affects the separate downloadFrom and webhook URL filtering paths.

PoC

One-command verification

From the repository root:

cd '/Users/r1zzg0d/Documents/CVE hunting/targets/gotenberg'
./tmp/poc/verify_ssrf_poc.sh

What the script does:

  1. Builds or reuses a slim local Gotenberg image that contains only the modules needed for this proof.
  2. Starts Gotenberg on 127.0.0.1:3000.
  3. Starts an internal-only helper listener inside the same container network namespace.
  4. Verifies downloadFrom SSRF by forcing Gotenberg to fetch a PDF from http://[::ffff:127.0.0.1]:18081/page_1.pdf.
  5. Verifies webhook SSRF by forcing Gotenberg to POST to http://[::ffff:127.0.0.1]:18082/upload and http://[::ffff:127.0.0.1]:18082/events.
  6. Writes evidence artifacts to disk.

Expected success output:

[4/6] Verifying downloadFrom SSRF bypass with http://[::ffff:127.0.0.1]:18081/page_1.pdf
PASS downloadFrom: Gotenberg fetched an internal-only loopback URL and returned PDF metadata
[5/6] Verifying webhook SSRF bypass with http://[::ffff:127.0.0.1]:18082/upload
PASS webhook: Gotenberg POSTed to an internal-only loopback listener

Evidence files created by the script:

  • /Users/r1zzg0d/Documents/CVE hunting/targets/gotenberg/tmp/poc/artifacts/downloadfrom-metadata.json
  • /Users/r1zzg0d/Documents/CVE hunting/targets/gotenberg/tmp/poc/artifacts/webhook.log

Manual evidence commands

The following commands were run after the verifier completed successfully:

jq '.' '/Users/r1zzg0d/Documents/CVE hunting/targets/gotenberg/tmp/poc/artifacts/downloadfrom-metadata.json'
cat…
Record
GHSA-4vmc-gm8v-m35h
CVSS 3.1
9.4 CriticalCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:L
Weakness
CWE-918
Updated
2026-11-02
OSVGO-2026-5132 No score

Gotenberg vulnerable to unauthenticated SSRF via default deny-list bypass in downloadFrom and webhook in github.com/gotenberg/gotenberg

Gotenberg vulnerable to unauthenticated SSRF via default deny-list bypass in downloadFrom and webhook in github.com/gotenberg/gotenberg

Record
GO-2026-5132
Updated
2026-11-02
OSVopenSUSE-SU-2026:21483-1 No score

Security update for govulncheck-vulndb

This update for govulncheck-vulndb fixes the following issues:

  • Update to version 0.0.20260723T184607 2026-07-23T18:46:07Z (jsc#PED-11136).

Go CVE Numbering Authority IDs added or updated with aliases:

  • GO-2026-4730 CVE-2026-33022 GHSA-cv4x-93xx-wgfj
  • GO-2026-4761 CVE-2026-33211 GHSA-j5q5-j9gm-2w5c
  • GO-2026-5102 CVE-2026-45021 GHSA-3vcp-chfh-f6r2
  • GO-2026-5272 CVE-2026-40938 GHSA-94jr-7pqp-xhcq
  • GO-2026-5486 CVE-2026-40924 GHSA-m2cx-gpqf-qf74
  • GO-2026-5542 CVE-2026-40090 GHSA-pj97-4p9w-gx3q
  • GO-2026-5630 CVE-2026-25542 GHSA-rmx9-2pp3-xhcr
  • GO-2026-5643 CVE-2026-40923 GHSA-rx35-6rhx-7858
  • GO-2026-5675 CVE-2026-41492 GHSA-vvf7-6rmr-m29q
  • GO-2026-5711 CVE-2026-40161 GHSA-wjxp-xrpv-xpff
  • GO-2026-5746 CVE-2026-41567 GHSA-x86f-5xw2-fm2r
  • GO-2026-5749 CVE-2026-41328 GHSA-x92x-px7w-4gx4
  • GO-2026-5837 CVE-2026-44840 GHSA-q2m9-6jp9-c6mc
  • GO-2026-5929 CVE-2026-44342 GHSA-26v7-h57m-gh9m
  • GO-2026-5930 CVE-2026-33655 GHSA-6qcr-qxgr-m7fv
  • GO-2026-5933 GHSA-3g4q-2f67-2gvh
  • GO-2026-5934 GHSA-59qp-cfj3-rp64
  • GO-2026-5935 GHSA-7856-g3gv-9wq8
  • GO-2026-5936 CVE-2026-53552 GHSA-26rh-24rg-j3vv
  • GO-2026-5937 CVE-2026-53508 GHSA-2jcc-mxv7-p3f9
  • GO-2026-5938 CVE-2026-53553 GHSA-4g5x-hcwm-82jw
  • GO-2026-5939 CVE-2026-10517 GHSA-698x-9w2p-7vvp
  • GO-2026-5940 CVE-2026-53572 GHSA-6w3m-4hhp-775q
  • GO-2026-5941 CVE-2026-53487 GHSA-gvhc-wv3v-7pf8
  • GO-2026-5942 CVE-2026-46600
  • GO-2026-5944 CVE-2026-50197 GHSA-659f-rgp5-w4wf
  • GO-2026-5945 CVE-2026-6815 GHSA-rmxx-v9rj-vpvg
  • GO-2026-5946 CVE-2026-52831 GHSA-v5px-423j-pf7p
  • GO-2026-5947 CVE-2026-53649 GHSA-xqhv-chqm-fhcc
  • GO-2026-5948 CVE-2026-50554 GHSA-588f-fvcv-xhvf
  • GO-2026-5949 CVE-2026-50553 GHSA-rqrh-8wpv-x7hh
  • GO-2026-5950 CVE-2026-53602 GHSA-339v-266x-79xr
  • GO-2026-5951 CVE-2026-10219 GHSA-6jm8-4fhr-5w64
  • GO-2026-5952 CVE-2026-49834 GHSA-9vcr-p3rj-q5q6
  • GO-2026-5953 CVE-2026-9094 GHSA-c9w5-qp6m-m395
  • GO-2026-5956 CVE-2026-55252 GHSA-h5g6-xmh4-hc37
  • GO-2026-5957 CVE-2026-54158 GHSA-5xfx-xj4h-5p7r
  • GO-2026-5958 CVE-2026-54068 GHSA-gcm7-57gf-953c
  • GO-2026-5959 CVE-2026-54072 GHSA-h29v-hj44-q8cv
  • GO-2026-5961 CVE-2026-54069 GHSA-hvr9-72v2-fff3
  • GO-2026-5962 CVE-2026-54088 GHSA-m93h-4hw7-5qcm
  • GO-2026-5963 CVE-2026-54067 GHSA-mvjr-vv3c-w4qv
  • GO-2026-5964 CVE-2026-54066 GHSA-p4m3-mgmm-c664
  • GO-2026-5965 CVE-2026-54070 GHSA-w7cg-whh7-xp28
  • GO-2026-5966 CVE-2026-54089 GHSA-xqp3-jq6g-x3qm
  • GO-2026-5967 CVE-2026-50551 GHSA-56mp-4f3v-fgj2
  • GO-2026-5968 CVE-2026-54174 GHSA-fpg8-7664-jc5q
  • GO-2026-5969 GHSA-g936-7jqj-mwv8
  • GO-2026-5970 CVE-2026-56852
  • GO-2026-5973 CVE-2026-54250 GHSA-jxr7-mqhw-9p98
  • GO-2026-5974 CVE-2026-44300 GHSA-wmj8-9953-vff5
  • GO-2026-5975 CVE-2026-50018 GHSA-42j2-w334-qxw7
  • GO-2026-5976 CVE-2026-50141 GHSA-g7mm-9vx7-jm7h
  • GO-2026-5977 CVE-2026-50013 GHSA-qrh4-p6v4-mrfg
  • GO-2026-5978 CVE-2026-50125 GHSA-qw5r-ppcg-f8rj
  • GO-2026-5979 CVE-2026-50006 GHSA-xrcf-6jh3-ggvx
  • GO-2026-5980 CVE-2026-50158 GHSA-2c7f-fxww-6w6c
  • GO-2026-5981 GHSA-mqxv-9rm6-w8qc
  • GO-2026-5982 GHSA-pqg7-v6wh-3pfp
  • GO-2026-5984 CVE-2026-53604 GHSA-2p2f-px33-4vv5
  • GO-2026-5985 GHSA-7rx3-5wx3-5v76
  • GO-2026-5986 CVE-2026-61699 GHSA-cm26-5974-52h8
  • GO-2026-5987 CVE-2026-55513 GHSA-g4x6-jcvr-9m3g
  • GO-2026-5988 CVE-2026-54628 GHSA-hwrq-8wxh-q4xv
  • GO-2026-5989 CVE-2026-55512 GHSA-m3cx-mwpg-32jg
  • GO-2026-5990 CVE-2026-54629 GHSA-mf78-3rpf-r784
  • GO-2026-5991 CVE-2026-53603 GHSA-q4vm-pq3q-8wgq
  • GO-2026-5992 CVE-2026-61549 GHSA-qf34-295c-26v8
  • GO-2026-5996 CVE-2026-54450 GHSA-pph6-vfjv-vpjw
  • GO-2026-5997 CVE-2026-54452 GHSA-xgch-x3mx-cm3c
  • GO-2026-5998 CVE-2026-54495 GHSA-398h-7f66-3h4p
  • GO-2026-5999 CVE-2026-10814 GHSA-jh6h-v6mp-h22v
  • GO-2026-6002 CVE-2026-58196 GHSA-pr64-jmmf-jp54
  • GO-2026-6003 CVE-2026-53714 GHSA-22xc-xg2r-9j7v
  • GO-2026-6004 CVE-2026-52833 GHSA-3v79-m2cg-89ww
  • GO-2026-6005 CVE-2026-53715 GHSA-8fv2-88gg-hm7q
  • GO-2026-6006 CVE-2026-53716 GHSA-cxpq-8v7q-cg56 *…
Record
openSUSE-SU-2026:21483-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
github.com/gotenberg/gotenberg/v8
Go
 through 8.30.1
8.32.0
github.com/gotenberg/gotenberg/v8
Go
 before 8.32.0
8.32.0
github.com/gotenberg/gotenberg/v7
Go
 All versions None known
govulncheck-vulndb
openSUSE:Leap 16.0
From an advisory covering 1734 CVEs
 before 0.0.20260723T184607-160000.1.1
0.0.20260723T184607-160000.1.1

Public exploits

Links only. Every CVE stores no exploit code.

Public exploits
SourceLinkDate
NucleiGotenberg < 8.31.0 - Server-Side Request Forgery

History

History
RecordedChangedSources
affected, facts
first indexedCVE List, EUVD, GitHub Advisories, Nuclei, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2026-42596 is a critical vulnerability (CVSS 9.4) in Gotenberg, published May 7, 2026. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 1.59%, the 75th percentile. Fixed in github.com/gotenberg/gotenberg/v8 8.32.0.

References

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