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Fencer Vulns
medium 5.0

CVE-2025-9799 json

Langfuse Webhook promptRouter.ts promptChangeEventSourcing server-side request forgery

published 2025-09-01 14 mo ago modified 2026-10-19 20 d ago also EUVD-2025-26361

cvss
5.0
version 3.1, CNA
cisa kev
Not listed
not in CISA's catalog
epss
0.3%
EPSS 0.3% chance of exploitation in 30 days, percentile 22%
public exploits
0
none known

Summary

A security flaw has been discovered in Langfuse up to 3.88.0. Affected by this vulnerability is the function promptChangeEventSourcing of the file web/src/features/prompts/server/routers/promptRouter.ts of the component Webhook Handler. Performing manipulation results in server-side request forgery. The attack may be initiated remotely. A high degree of complexity is needed for the attack. The exploitation appears to be difficult. The exploit has been released to the public and may be exploited.

CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
14 mo ago

Exploit prediction

0.30% chance of exploitation in the next 30 days, higher than 22% of all scored CVEs (FIRST EPSS, 2026-11-08).

Exploits and checks

  • github.com https://github.com/langfuse/langfuse/issues/8522#issue-3320549867 referenced PoC, tagged "exploit" by a source, unverified
  • github.com https://github.com/langfuse/langfuse/issues/8522 referenced PoC, tagged "exploit" by a source, unverified

CVSS scores

assigned by version score vector
CNA 4.0 2.3 CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P
CNA 3.1 5.0 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L/E:P/RL:X/RC:R
CNA 3.0 5.0 CVSS:3.0/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L/E:P/RL:X/RC:R
CNA 2.0 4.6 AV:N/AC:H/Au:S/C:P/I:P/A:P/E:POC/RL:ND/RC:UR
CNA 4.0 1.3 CVSS:4.0/AV:N/AC:H/AT:N/PR:L/UI:N/VC:L/VI:L/VA:L/SC:N/SI:N/SA:N/E:P/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
CNA 3.1 5.0 CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:U/C:L/I:L/A:L
CNA 2.0 4.6 AV:N/AC:H/Au:S/C:P/I:P/A:P

Affected products

  • n/a Langfuse

Classification

Weakness
  • CWE-918 Server-Side Request Forgery

References

Sources

Fencer Vulns keeps one entry per vulnerability: the CVE id wins, then GHSA, and records that alias each other are merged, except that two CVEs always keep separate entries. The same data is available as JSON.