CVE-2024-37894Public exploitNetwork attack vector

Proxy crash via negative ESI trie index

Published Jun 25, 2024 · Updated Nov 3, 2025

Out-of-bounds write in ESI processing in Squid allows remote attackers controlling a trusted origin to crash the proxy via crafted content. TrieNode::add converts non-ASCII bytes from an esi:assign variable name to signed integer indexes and writes before its internal pointer array. Reachability requires Squid to act as a reverse proxy with ESI compiled in; a crash interrupts every domain and client using that proxy.

CVSS severity6.3
Medium
EPSS probability6.25%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
Coverage for this vulnerability

See if you're affected

Explore vulnerability checks for your environment with Hinoki.

Book a demo

Summary

What happened

Out-of-bounds write in ESI processing in Squid allows remote attackers controlling a trusted origin to crash the proxy via crafted content. TrieNode::add converts non-ASCII bytes from an esi:assign variable name to signed integer indexes and writes before its internal pointer array. Reachability requires Squid to act as a reverse proxy with ESI compiled in; a crash interrupts every domain and client using that proxy.

The record

CVE
CVE-2024-37894
Published
Jun 25, 2024
Updated
Nov 3, 2025
Vendor
The Squid Software Foundation
Product
Squid
Classifications
CWE-787, T1499.004
Attack vector
network
Privileges
authenticated

Timeline

How it unfolded

  1. Jun 25, 2024CVE publishedPublication date reported by the CVE source.
  2. Nov 3, 2025Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

Compare your product and version with the public record. A matching version still requires validation against your environment.

Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=>= 3.0, <= 3.5.28
  2. Affected versionversion=>= 4.0, <= 4.16
  3. Affected versionversion=>= 5.0, <= 5.9
  4. Affected versionversion=>= 6.0, <= 6.9

What conditions does exploitation require?

Attack vectornetwork
Required privilegesauthenticated

What is affected?

The Squid Software Foundation · Squidversion=>= 3.0, <= 3.5.28; version=>= 4.0, <= 4.16; version=>= 5.0, <= 5.9; version=>= 6.0, <= 6.9

Published CVSS scores

6.3GitHub, Inc.CVSS:3.1/AV:N/AC:H/PR:L/UI:N/S:C/C:N/I:N/A:H

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

Daily unique IPsNo honeypot observations are available for this CVE in the selected window.

No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-787Out-of-bounds Write
T1499.004Application or System Exploitation

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

See the directory against your own environment.

Your stack

Check the software in your environment

Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.

Book a demo