← Vulnerability feed

Vulnerability record · CVE-2009-2622 · published 28 July 2009

CVE-2009-2622: Squid proxy input validation flaw allows remote denial of service

Squid Cache · Squid

Squid 3.0 through 3.0.STABLE16 and 3.1 through 3.1.0.11 fail to properly validate malformed HTTP requests and replies, including missing or mismatched protocol identifiers, missing or negative status values, missing versions, and missing or invalid status numbers. The flaw is in HttpMsg.cc and HttpReply.cc, and a remote attacker can crash or disrupt the proxy service.

5.0 CVSS 2.0 Medium EPSS 57% · top 1.0% CWE-20 · Improper input validation
5.0CVSS 2.0 base score
57%EPSS exploitation probability, 30 days
NoNot in CISA KEV
1Affected product versions listed by NVD
16References
16 Jun 2026Last modified by NVD

Description

Squid 3.0 through 3.0.STABLE16 and 3.1 through 3.1.0.11 allows remote attackers to cause a denial of service via malformed requests including (1) "missing or mismatched protocol identifier," (2) missing or negative status value," (3) "missing version," or (4) "missing or invalid status number," related to (a) HttpMsg.cc and (b) HttpReply.cc.

AV:N/AC:L/Au:N/C:N/I:N/A:P

Automated analysis

Generated by VULONE's analysis model from the NVD record, CISA KEV and EPSS data on 19 September 2026. Confidence: high.

medium priorityThe flaw is remotely reachable without authentication and has high EPSS, but it only causes denial of service with no confidentiality or integrity impact and a CVSS base score of 5.0.

What it is

Squid 3.0 through 3.0.STABLE16 and 3.1 through 3.1.0.11 fail to properly validate malformed HTTP requests and replies, including missing or mismatched protocol identifiers, missing or negative status values, missing versions, and missing or invalid status numbers. The flaw is in HttpMsg.cc and HttpReply.cc, and a remote attacker can crash or disrupt the proxy service.

Impact

An unauthenticated remote attacker can cause a denial of service against the Squid proxy, interrupting web access for all users relying on it. There is no confidentiality or integrity impact per the CVSS vector.

Attack surface

The flaw is reachable over the network via malformed HTTP requests or replies processed by Squid; the CVSS vector AV:N/AC:L/Au:N indicates no authentication and no user interaction are required.

Exploitation

Not listed in CISA KEV and no public exploit references are tagged in the record, but EPSS is 0.56908 (99th percentile), indicating a high predicted likelihood of exploitation activity.

What to do

  • Apply the vendor patch referenced in the Squid advisory SQUID-2009_2 and changeset b9661, or upgrade to a fixed Squid release.
  • Restrict network access to Squid proxy ports to trusted clients where feasible.
  • Monitor vendor and distribution advisories (Mandriva MDVSA-2009:161 and MDVSA-2009:178) for packaged updates.
  • If patching is delayed, consider rate limiting or filtering malformed HTTP traffic at the network edge.

Detection

  • Monitor Squid logs for crashes, restarts, or abnormal termination correlated with malformed HTTP requests.
  • Inspect proxy traffic for requests with missing or mismatched protocol identifiers, missing versions, or invalid status values.
  • Alert on repeated malformed request patterns from a single source IP targeting the proxy.
  • Track service availability of Squid instances for unexplained outages.

This assessment is produced automatically and is not human-reviewed. Verify against the vendor advisory before acting on it.

Affected products

1 vulnerable configurations from NVD's CPE data, grouped by vendor and product.

References

LinkTags
http://secunia.com/advisories/36007
http://www.mandriva.com/security/advisories?name=MDVSA-2009:161
http://www.mandriva.com/security/advisories?name=MDVSA-2009:178
http://www.securityfocus.com/bid/35812
http://www.securitytracker.com/id?1022607
http://www.squid-cache.org/Advisories/SQUID-2009_2.txt Vendor Advisory
http://www.squid-cache.org/Versions/v3/3.1/changesets/b9661.patch PatchVendor Advisory
http://www.vupen.com/english/advisories/2009/2013
http://secunia.com/advisories/36007
http://www.mandriva.com/security/advisories?name=MDVSA-2009:161
http://www.mandriva.com/security/advisories?name=MDVSA-2009:178
http://www.securityfocus.com/bid/35812
http://www.securitytracker.com/id?1022607
http://www.squid-cache.org/Advisories/SQUID-2009_2.txt Vendor Advisory
http://www.squid-cache.org/Versions/v3/3.1/changesets/b9661.patch PatchVendor Advisory
http://www.vupen.com/english/advisories/2009/2013

Track CVE-2009-2622 inside VULONE

Watch it alongside the ransomware crews, C2 infrastructure and forum chatter that reference it, query it through the API and pull it into your SIEM over TAXII.

Start free Open in platform

Related vulnerabilities

Same products first, then exploited flaws of the same weakness class.

9.8CVE-2025-54574Squid-cache squid heap-based buffer overflow vulnerabilitySquid is a caching proxy for the Web. In versions 6.3 and below, Squid is vulnerable to a heap buffer overflow and possible remote code execution att…EPSS 23%9.8CVE-2020-11945Squid-cache squid integer overflow vulnerabilityAn issue was discovered in Squid before 5.0.2. A remote attacker can replay a sniffed Digest Authentication nonce to gain access to resources that ar…EPSS 27%9.8CVE-2019-12519Squid-cache squid out-of-bounds write vulnerabilityAn issue was discovered in Squid through 4.7. When handling the tag esi:when when ESI is enabled, Squid calls ESIExpression::Evaluate. This function …EPSS 6.7%9.8CVE-2019-12524Squid-cache squid missing authentication for critical function vulnerabilityAn issue was discovered in Squid through 4.7. When handling requests from users, Squid checks its rules to see if the request should be denied. Squid…EPSS 4.3%9.8CVE-2019-12526Squid-cache squid out-of-bounds write vulnerabilityAn issue was discovered in Squid before 4.9. URN response handling in Squid suffers from a heap-based buffer overflow. When receiving data from a rem…EPSS 20%9.8CVE-2019-12525Squid-cache squid out-of-bounds write vulnerabilityAn issue was discovered in Squid 3.3.9 through 3.5.28 and 4.x through 4.7. When Squid is configured to use Digest authentication, it parses the heade…EPSS 24%9.2CVE-2026-33526Squid-cache squid use after free vulnerabilitySquid is a caching proxy for the Web. Prior to version 7.5, due to heap Use-After-Free, Squid is vulnerable to Denial of Service when handling ICP tr…EPSS 13%9.1CVE-2019-12523Squid-cache squid vulnerabilityAn issue was discovered in Squid before 4.9. When handling a URN request, a corresponding HTTP request is made. This HTTP request doesn't go through …EPSS 4.3%

Source: NIST National Vulnerability Database (record CVE-2009-2622), CISA KEV, FIRST EPSS (scores of 2026-09-26). This page is refreshed as NVD updates the record.