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CVE-2019-16786

HIGHCVSS 7.5/10EPSS 2.54%

Last modified

CVE-2019-16786 is a high-severity vulnerability rated 7.5/10 on the CVSS scale. Waitress through version 1.3.1 would parse the Transfer-Encoding header and only look for a single string value, if that value was not chunked it would fall through and use the Content-Length header instead. According to the HTTP standard Transfer-Encoding should be a comma separated list, with the inner-most encoding first, followed by any further transfer codings, ending with chunked. EPSS estimates a 2.54% chance of exploitation in the next 30 days.

Description

Waitress through version 1.3.1 would parse the Transfer-Encoding header and only look for a single string value, if that value was not chunked it would fall through and use the Content-Length header instead. According to the HTTP standard Transfer-Encoding should be a comma separated list, with the inner-most encoding first, followed by any further transfer codings, ending with chunked. Requests sent with: "Transfer-Encoding: gzip, chunked" would incorrectly get ignored, and the request would use a Content-Length header instead to determine the body size of the HTTP message. This could allow for Waitress to treat a single request as multiple requests in the case of HTTP pipelining. This issue is fixed in Waitress 1.4.0.

Metrics

CVSS 3.1
7.5/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

EPSS Probability
2.54%

83.0th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
AgendalessWaitress< 1.3.1
OracleCommunications Cloud Native Core Network Function Cloud Native Environment1.10.0
DebianDebian Linux9.0
FedoraprojectFedora30
FedoraprojectFedora31
RedhatOpenstack15

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2019-16786?
Waitress through version 1.3.1 would parse the Transfer-Encoding header and only look for a single string value, if that value was not chunked it would fall through and use the Content-Length header instead. According to the HTTP standard Transfer-Encoding should be a comma separated list, with the inner-most encoding first, followed by any further transfer codings, ending with chunked. Requests sent with: "Transfer-Encoding: gzip, chunked" would incorrectly get ignored, and the request would use a Content-Length header instead to determine the body size of the HTTP message. This could allow for Waitress to treat a single request as multiple requests in the case of HTTP pipelining. This issue is fixed in Waitress 1.4.0.
How severe is CVE-2019-16786?
CVE-2019-16786 has a CVSS score of 7.5/10 (HIGH severity). The EPSS model estimates a 2.54% probability of exploitation in the next 30 days.
How do I fix CVE-2019-16786?
Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2019-16786?

Run a free Strix scan to check your systems for this vulnerability.

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Source: NVD / NIST