CVE-2023-45539 — HAProxy before 2

HAProxy before 2.8.2 accepts # as part of the URI component, which might allow remote attackers to obtain sensitive information or have unspecified other impact upon misinterpretation of a path_end rule, such as routing index.html#.png to a static server.

01What is this vulnerability?

HAProxy before 2.8.2 accepts # as part of the URI component, which might allow remote attackers to obtain sensitive information or have unspecified other impact upon misinterpretation of a path_end rule, such as routing index.html#.png to a static server.

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: 2023-11-28T00:00:00.000Z
• Last modified: 2024-10-15T17:44:03.661Z

09References

• lists.w3.org — https://lists.w3.org/Archives/Public/ietf-http-wg/2023JulSep/0070.html
• git.haproxy.org — https://git.haproxy.org/?p=haproxy.git%3Ba=commit%3Bh=2eab6d354322932cfec2ed54de…
• www.mail-archive.com — https://www.mail-archive.com/haproxy%40formilux.org/msg43861.html
• lists.debian.org — https://lists.debian.org/debian-lts-announce/2023/12/msg00010.html