CVE-2019-18277 — A flaw was found in HAProxy before 2

A flaw was found in HAProxy before 2.0.6. In legacy mode, messages featuring a transfer-encoding header missing the "chunked" value were not being correctly rejected. The impact was limited but if combined with the "http-reuse always" setting, it could be used

01What is this vulnerability?

A flaw was found in HAProxy before 2.0.6. In legacy mode, messages featuring a transfer-encoding header missing the "chunked" value were not being correctly rejected. The impact was limited but if combined with the "http-reuse always" setting, it could be used to help construct an HTTP request smuggling attack against a vulnerable component employing a lenient parser that would ignore the…

02Affected products

Vendor	Product	Versions
n	a / n/a	n/a

03Active exploitation status

Not currently listed on the CISA Known Exploited Vulnerabilities (KEV) catalog. EPSS is the best forward-looking signal — see the EPSS row above.

04Recommended remediation

• Patch to a fixed version listed in the vendor advisory (see references below).
• Mitigate with WAF rules, network egress filters, or feature flags where the patch is not yet available.
• Hunt historical logs for exploitation indicators — see Detection signatures below.

05Technical details

For the full vendor write-up, exploit chains, and reference implementations, see the references list in section 09.

06Detection signatures

Ask SARA in chat to draft a starting detection for this CVE in your stack of choice.

07Related CVEs

No directly-cited follow-up CVEs in the KB record for this advisory. The references list in section 09 carries the vendor cross-references.

08Timeline

• Published: 2019-10-23T13:07:01.000Z
• Last modified: 2024-08-05T01:47:14.151Z

09References

• www.mail-archive.com — https://www.mail-archive.com/haproxy%40formilux.org/msg34926.html
• nathandavison.com — https://nathandavison.com/blog/haproxy-http-request-smuggling
• git.haproxy.org — https://git.haproxy.org/?p=haproxy-2.0.git%3Ba=commit%3Bh=196a7df44d8129d1adc795…
• usn.ubuntu.com — https://usn.ubuntu.com/4174-1/
• lists.opensuse.org — http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00016.html
• lists.opensuse.org — http://lists.opensuse.org/opensuse-security-announce/2019-12/msg00019.html
• lists.debian.org — https://lists.debian.org/debian-lts-announce/2022/05/msg00045.html