# CVE-2026-51583: Memos Server-Side Request Forgery in webhook validation

Source: https://junglewise.ai/threats/cve-2026-51583-memos-server-side-request-forgery-in-webhook-validation  
Publisher: Junglewise Threat Intelligence, https://junglewise.ai/threats  
Published: 2026-08-11. Updated: 2026-09-25  
License: CC BY 4.0 with a link back

CVE-2026-51583 · Severity: high · CVSS 8.5 · Published 2026-08-11

Memos is an open-source note-taking application that allows users to configure webhooks to trigger external HTTP requests when memo events occur. An authenticated attacker can bypass the webhook URL validation mechanism by pointing webhooks at internal network addresses (e.g., 0.0.0.0, CGNAT ranges, or link-local addresses), causing the Memos server to make HTTP POST requests to services that should not be accessible from outside the internal network, potentially exposing or compromising cloud metadata endpoints, internal admin panels, or other containerized services.

Technologies: [Usememos Memos](https://junglewise.ai/threats/technologies/memos). Vendors: [Usememos](https://junglewise.ai/threats/vendors/usememos).

## Quick answers

**Is CVE-2026-51583 exploited in the wild?** No. Junglewise Threat Intelligence has no report of CVE-2026-51583 being exploited in the wild.

**How severe is CVE-2026-51583?** High severity, with a CVSS score of 8.5, published 11 August 2026.

**Which products and versions are affected?** Usememos Memos through v0.30.0.

**Is there a fix for CVE-2026-51583?** No fixed version is recorded yet. Check the vendor's advisory in the references below. If you run it, Junglewise drafts a mitigation that fits your setup and applies it once you approve, with senior security engineers behind it.

**How is CVE-2026-51583 attacked?** It is attacked over the network, in a web application.

**Am I affected by CVE-2026-51583?** Check whether you run Usememos Memos at an affected version. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

## Technical details

The vulnerability is a Server-Side Request Forgery (SSRF) in the webhook validation mechanism (internal/webhook/validate.go). The isReservedIP() predicate used to block internal addresses maintains an incomplete reservedCIDRs list that omits 0.0.0.0/8 (unspecified), ::/128 (IPv6 unspecified), 100.64.0.0/10 (CGNAT), 192.0.0.0/24 (IETF protocol assignments), 198.18.0.0/15 (benchmarking), and multicast ranges. An authenticated user can register a webhook targeting any of these omitted ranges; when a memo event fires, the backend dispatches an HTTP POST from within the internal network boundary to the attacker-specified address. The predicate is reused at both registration and dispatch time, so a gap in the list bypasses both validation layers simultaneously. No patch was available as of v0.30.0; the advisory recommends using Go's built-in net.IP predicates (IsUnspecified, IsLoopback, IsPrivate, IsLinkLocalUnicast) combined with explicit blocks for the omitted CIDR ranges.

## Affected products

- usememos Memos through v0.30.0

## Timeline

- 2026-08-11: disclosed: CVE-2026-51583 published; no upstream patch available at time of publication
- 2026-02-23: other: Incomplete SSRF remediation introduced in v0.26.2/v0.27.0 (commit 150371d2)

## References

- [https://gist.github.com/seiyaibuki0523/d8af15eb555808319a2633269a9ebb80](https://gist.github.com/seiyaibuki0523/d8af15eb555808319a2633269a9ebb80)
- [https://github.com/usememos/memos](https://github.com/usememos/memos)

## Related threats

- [Memos missing authorization in ActivityService API methods](https://junglewise.ai/threats/cve-2026-113601-memos-before-0-27-0-contains-a-missing-authorization)
- [Memos link-metadata fetcher SSRF via missing carrier-grade NAT range](https://junglewise.ai/threats/cve-2026-82476-memos-link-metadata-fetcher-ssrf-via-missing-carrier-grade-nat)
- [usememos Memos SSO account takeover via identifier mismatch](https://junglewise.ai/threats/cve-2026-51584-usememos-memos-sso-account-takeover-via-identifier-mismatch)
- [usememos Memos HTML injection and UI redressing in SANITIZE_SCHEMA](https://junglewise.ai/threats/cve-2026-30586-usememos-memos-html-injection-and-ui-redressing-in-sanitize)
- [usememos Memos incorrect privilege assignment in UpdateInstanceSetting](https://junglewise.ai/threats/cve-2026-6634-usememos-memos-incorrect-privilege-assignment-in)