CyberSecBulletin
CVE-2023-25725NVD status: Modified

Haproxy: Inconsistent Interpretation of HTTP Requests

Published Updated By the CyberSecBulletin desk

CVE-2023-25725 is a critical-severity inconsistent interpretation of HTTP requests vulnerability in Haproxy, with a CVSS 3.1 base score of 9.1 out of 10. It can be exploited remotely over the network by an unauthenticated attacker, without any action from a user. The record lists versions 2.0.31, 2.2.29, 2.4.22 as the first without the flaw, so updating Haproxy to one of those releases or later removes the exposure. There is no confirmed exploitation so far. EPSS estimates a 5.49% chance of exploitation within 30 days, which is in the top 7.09% of all scored CVEs.

Patch this week

Critical severity: a successful attack would have severe impact.

What to do

  1. Update Haproxy to 2.0.31 or 2.2.29 or 2.4.22 or 2.5.12, whichever matches your release line, or a later version.
  2. Until you can update, restrict network access to the affected service so it is not reachable from untrusted networks.

Affected products and versions

VendorProductAffected versionsFixed in
HaproxyHaproxybefore 2.0.31; 2.1.0 up to, but not including, 2.2.29; 2.3.0 up to, but not including, 2.4.22; 2.5.0 up to, but not including, 2.5.12; 2.6.0 up to, but not including, 2.6.9; 2.7.0 up to, but not including, 2.7.32.0.31, 2.2.29, 2.4.22, 2.5.12, 2.6.9, 2.7.3
DebianDebian Linux10.0; 11.0Not stated

Version data comes from NVD's product matching. Confirm against the vendor advisory before deciding you are unaffected.

How the severity score breaks down

Attack vector
NetworkCan be exploited remotely over a network, including the internet.
Attack complexity
LowNo special conditions are needed; the attack works reliably.
Privileges required
NoneNo account or login is needed.
User interaction
NoneNo action by a victim is required.
Scope
UnchangedImpact stays within the vulnerable component.
Confidentiality
NoneNo data is disclosed.
Integrity
HighData or code can be modified at will.
Availability
HighThe component can be taken down completely.

Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H. Scored by NVD.

Scoring systemScoreSeverityScored by
CVSS 3.19.1CriticalNVD
CVSS 3.19.1CriticalCISA (ADP)

Official description

HAProxy before 2.7.3 may allow a bypass of access control because HTTP/1 headers are inadvertently lost in some situations, aka "request smuggling." The HTTP header parsers in HAProxy may accept empty header field names, which could be used to truncate the list of HTTP headers and thus make some headers disappear after being parsed and processed for HTTP/1.0 and HTTP/1.1. For HTTP/2 and HTTP/3, the impact is limited because the headers disappear before being parsed and processed, as if they had not been sent by the client. The fixed versions are 2.7.3, 2.6.9, 2.5.12, 2.4.22, 2.2.29, and 2.0.31.

Source: the CVE record as published by its numbering authority, via NVD and CVE.org.

The underlying weakness: Inconsistent Interpretation of HTTP Requests

The product acts as an intermediary HTTP agent (such as a proxy or firewall) in the data flow between two entities such as a client and server, but it does not interpret malformed HTTP requests or responses in ways that are consistent with how the messages will be processed by those entities that are at the ultimate destination.

How developers prevent this class of flaw

  • Use a web server that employs a strict HTTP parsing procedure, such as Apache.
  • Terminate the client session after each request.

More Inconsistent Interpretation of HTTP Requests vulnerabilities (CWE-444)

Timeline

  1. CVE record published.
  2. CISA published its SSVC assessment (exploitation: none, automatable: yes, technical impact: partial).
  3. Record last changed materially (score, affected products, status or references).

References

Third-party and government advisories

Other vulnerabilities in Haproxy

All Haproxy vulnerabilities

Recent Inconsistent Interpretation of HTTP Requests vulnerabilities

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