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Fencer Intel
medium 5.0

CVE-2025-9799 json

Langfuse Webhook promptRouter.ts promptChangeEventSourcing server-side request forgery

published last yr. modified 21d 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.

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CISA SSVC

Exploitation
Proof of concept is public
Automatable
no
Technical impact
partial
Assessed
last yr.

Exploit prediction

0.30% chance of exploitation in the next 30 days, higher than 22% of all scored CVEs (FIRST EPSS, 2026-11-09).

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 Intel 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.