Debian LinuxOperating system · Debian
CVE-2023-25725
Official description Straight from the sourceThe vendor's or NVD's own wording, published unedited. Authoritative, but often terse — it says what broke, rarely what to do.
NVD · uneditedHAProxy 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.
Technical summary Written by usOur analysis, written from the advisory, the CVSS vector and the affected-version data. It adds context the advisory leaves out, and never invents facts that are not in the source.
dbcve analysis · high confidenceHAProxy before 2.7.3 contains a request smuggling vulnerability where HTTP/1 header parsers accept empty header field names, allowing attackers to truncate the header list and cause legitimate headers to disappear after parsing. This enables bypass of access controls in HTTP/1.0 and HTTP/1.1 connections.
Verify against the referenced sources before acting — the references below are authoritative for this CVE, this summary is not.
Affected products & versions What the vendor confirmedThe version ranges the vendor confirmed as vulnerable. If your version sits inside a range here, treat yourself as exposed until you have upgraded.
NVD · CPE data
Debian LinuxOperating system
= 10.0= 11.0< 2.0.31>= 2.1.0, < 2.2.29>= 2.3.0, < 2.4.22>= 2.5.0, < 2.5.12>= 2.6.0, < 2.6.9>= 2.7.0, < 2.7.3CVSS breakdown How the score is builtThe industry scoring standard. It rates how the flaw is reached, what it takes to exploit, and what an attacker gains — the score is derived from those, not the other way round.
From the vector- Attack vector
- Network
- Complexity
- Low
- Privileges
- None
- User interaction
- None
- Scope
- Unchanged
- Confidentiality
- None
- Integrity
- High
- Availability
- High
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:H
Am I affected? How to checkSteps we derive from the advisory and the affected-version data, so you can decide whether this CVE reaches your setup. They are a guide, not a scan — your own configuration is the authority.
dbcve checksWork through these to decide whether this CVE applies to you.
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Check installed HAProxy versionRun `haproxy -v` or `haproxy --version` to display the version. On Debian, also check `dpkg -l haproxy` or `apt-cache policy haproxy`.Affected if The version number is less than 2.0.31, OR between 2.1.0 and 2.2.28 inclusive, OR between 2.3.0 and 2.4.21 inclusive, OR between 2.5.0 and 2.5.11 inclusive, OR between 2.6.0 and 2.6.8 inclusive, OR between 2.7.0 and 2.7.2 inclusive.
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Verify HTTP/1 frontends are in useExamine HAProxy configuration files (typically in /etc/haproxy/) and look for `frontend` sections with `http` mode or `bind` directives using HTTP/1 ports (80, 443, or custom HTTP ports).Affected if Any frontend is configured to handle HTTP/1.0 or HTTP/1.1 traffic (this is the default mode when `mode http` is used).
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Confirm HAProxy is exposing HTTP servicesReview the HAProxy configuration for `bind` statements accepting HTTP connections. Check if there are any frontends with `mode http` that accept traffic on HTTP or HTTPS ports.Affected if HAProxy is configured to accept HTTP/1 connections on any port, because the vulnerability lies in the HTTP/1 header parser.
You are affected if your HAProxy version falls within any of the vulnerable version ranges AND you have HTTP/1 frontends or backends configured, which is the default configuration for HTTP traffic handling.
Generated from the published advisory. Verify against your own configuration.
Remediation Closing itWhat it takes to close this. Where a vendor fix exists we point at it; where none exists we say so plainly, and can build one. Effort estimates are scoped from the advisory, not from your codebase.
dbcve · scoped2.0.312.2.292.4.22
Upgrade HAProxy to version 2.7.3 or later (or one of the other fixed versions: 2.6.9, 2.5.12, 2.4.22, 2.2.29, or 2.0.31) to patch this vulnerability.
Upgrade to 2.5.12 (latest fixed branch), or to the appropriate fixed version for your current branch: 2.0.31, 2.2.29, 2.4.22, or 2.5.12
- 1. Identify current HAProxy version using 'haproxy -v' or 'haproxy -V'
- 2. Determine which version branch currently runs (e.g., 2.0.x, 2.2.x, 2.3.x, 2.4.x, 2.5.x)
- 3. For Debian 10/11: Run 'apt update && apt list --upgradable' to check available packages
- 4. Upgrade to the fixed version for your branch: 2.0.31, 2.2.29, 2.4.22, or 2.5.12 respectively
- 5. On Debian: 'apt install haproxy=<fixed-version>' or 'apt upgrade haproxy'
- 6. Backup current config: 'cp /etc/haproxy/haproxy.cfg /etc/haproxy/haproxy.cfg.bak'
- 7. Reload HAProxy: 'systemctl reload haproxy' or 'haproxy -f /etc/haproxy/haproxy.cfg -sf $(cat /var/run/haproxy.pid)'
- 8. Verify version: 'haproxy -v' confirms the new version is running
Generated from the published advisory — verify against the referenced sources before acting.
Fix this in Debian Linux
Scoped from the published advisory
- Consultation1.0 h
- Implementation2.0 h
- Testing4.0 h
- Review / QA1.0 h
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Scan for this in your stack
Free · runs locallyCheck whether your project pulls in CVE-2023-25725 — or any other known-vulnerable package — straight from your lock files. Free and open source; it runs locally and uploads nothing.
References Go to the primary sourcePrimary sources — vendor advisories, patches and trackers. Where our summary and a reference disagree, the reference wins.
Primary sourcesPractitioner notes
ContributedPeer-ranked notes from engineers who’ve handled CVE-2023-25725 in production — separate from our analysis above.
The advisory tells you what broke. It rarely tells you what actually worked. If you’ve dealt with this one, that detail is what the next engineer is searching for.
- The version that genuinely resolved it — not the one the vendor claimed
- A config change or rule that shut the vector down
- A gotcha in the upgrade path that cost you an afternoon
No notes yet
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- Version or environment caveats, and links to real fixes
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