CVE-2025-5399

Published Jun 7, 2025

Last updated 9 months ago

CVSS high 7.5
Libcurl

Overview

Description
Due to a mistake in libcurl's WebSocket code, a malicious server can send a particularly crafted packet which makes libcurl get trapped in an endless busy-loop. There is no other way for the application to escape or exit this loop other than killing the thread/process. This might be used to DoS libcurl-using application.
Source
2499f714-1537-4658-8207-48ae4bb9eae9
NVD status
Analyzed
Products
curl

Risk scores

CVSS 3.1

Type
Secondary
Base score
7.5
Impact score
3.6
Exploitability score
3.9
Vector string
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Severity
HIGH

Weaknesses

nvd@nist.gov
CWE-835

Social media

Hype score
Not currently trending

  1. CVE-2025-5399 (CVSS:7.5, HIGH) is Awaiting Analysis. Due to a mistake in libcurl's WebSocket code, a malicious server can send a particularly crafted packet which makes libc..https://t.co/RPaztPDu5X #cybersecurityawareness #cybersecurity #CVE #infosec #hacker #nvd #mitre

    @cracbot

    12 Jun 2025

    9 Impressions

    0 Retweets

    0 Likes

    0 Bookmarks

    0 Replies

    0 Quotes

  2. 🚨Une faille sévère dans cURL permet de provoquer un déni de service (DoS) à distance. 🔒 Bulletin de sécurité cURL du 4 juin 2025 – Vulnérabilité critique CVE-2025-5399. https://t.co/3PWUI0IwJV

    @NicolasCoolman

    8 Jun 2025

    25 Impressions

    0 Retweets

    0 Likes

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    0 Replies

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  3. ⚡ CVE-2025-5399: WebSocket endless loop 👨🏻‍💻 z2_ ➟ curl 🟨 Low 💰 None 🔗 https://t.co/0Ma0GLQ2YP #bugbounty #bugbountytips #cybersecurity #infosec https://t.co/H1aWHxKoDx

    @h1Disclosed

    4 Jun 2025

    869 Impressions

    2 Retweets

    10 Likes

    3 Bookmarks

    0 Replies

    0 Quotes

Configurations

Related CVEs

  1. When an OAuth2 bearer token is used for an HTTP(S) transfer, and that transfer performs a redirect to a second URL, curl could leak that token to the second hostname under some circumstances. If the hostname that the first request is redirected to has information in the used .netrc file, with either of the `machine` or `default` keywords, curl would pass on the bearer token set for the first host also to the second one.•CVE-2026-3783
  2. curl would wrongly reuse an existing HTTP proxy connection doing CONNECT to a server, even if the new request uses different credentials for the HTTP proxy. The proper behavior is to create or use a separate connection.•CVE-2026-3784
  3. When doing a second SMB request to the same host again, curl would wrongly use a data pointer pointing into already freed memory.•CVE-2026-3805
  4. libcurl can in some circumstances reuse the wrong connection when asked to do an Negotiate-authenticated HTTP or HTTPS request. libcurl features a pool of recent connections so that subsequent requests can reuse an existing connection to avoid overhead. When reusing a connection a range of criterion must first be met. Due to a logical error in the code, a request that was issued by an application could wrongfully reuse an existing connection to the same server that was authenticated using different credentials. One underlying reason being that Negotiate sometimes authenticates *connections* and not *requests*, contrary to how HTTP is designed to work. An application that allows Negotiate authentication to a server (that responds wanting Negotiate) with `user1:password1` and then does another operation to the same server also using Negotiate but with `user2:password2` (while the previous connection is still alive) - the second request wrongly reused the same connection and since it then sees that the Negotiate negotiation is already made, it just sends the request over that connection thinking it uses the user2 credentials when it is in fact still using the connection authenticated for user1... The set of authentication methods to use is set with `CURLOPT_HTTPAUTH`. Applications can disable libcurl's reuse of connections and thus mitigate this problem, by using one of the following libcurl options to alter how connections are or are not reused: `CURLOPT_FRESH_CONNECT`, `CURLOPT_MAXCONNECTS` and `CURLMOPT_MAX_HOST_CONNECTIONS` (if using the curl_multi API).•CVE-2026-1965
  5. URLs containing percent-encoded slashes (`/` or `\`) can trick wcurl into saving the output file outside of the current directory without the user explicitly asking for it. This flaw only affects the wcurl command line tool.•CVE-2025-11563

References

Sources include official advisories and independent security research.