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CVE-2020-15811

MEDIUMCVSS 6.5/10EPSS 4.23%

Last modified

CVE-2020-15811 is a medium-severity vulnerability rated 6.5/10 on the CVSS scale. An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP Request Splitting attacks may succeed against HTTP and HTTPS traffic. EPSS estimates a 4.23% chance of exploitation in the next 30 days.

Description

An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP Request Splitting attacks may succeed against HTTP and HTTPS traffic. This leads to cache poisoning. This allows any client, including browser scripts, to bypass local security and poison the browser cache and any downstream caches with content from an arbitrary source. Squid uses a string search instead of parsing the Transfer-Encoding header to find chunked encoding. This allows an attacker to hide a second request inside Transfer-Encoding: it is interpreted by Squid as chunked and split out into a second request delivered upstream. Squid will then deliver two distinct responses to the client, corrupting any downstream caches.

Metrics

CVSS 3.1
6.5/10

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

EPSS Probability
4.23%

89.8th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

Affected Software

VendorProductVersions
Squid-CacheSquid< 4.13
Squid-CacheSquid>= 5.0, < 5.0.4
CanonicalUbuntu Linux16.04
CanonicalUbuntu Linux18.04
CanonicalUbuntu Linux20.04
DebianDebian Linux9.0
DebianDebian Linux10.0
FedoraprojectFedora31
FedoraprojectFedora32
FedoraprojectFedora33
OpensuseLeap15.1
OpensuseLeap15.2

References

Timeline

Published
Last Modified
Status
Modified

Frequently Asked Questions

What is CVE-2020-15811?
An issue was discovered in Squid before 4.13 and 5.x before 5.0.4. Due to incorrect data validation, HTTP Request Splitting attacks may succeed against HTTP and HTTPS traffic. This leads to cache poisoning. This allows any client, including browser scripts, to bypass local security and poison the browser cache and any downstream caches with content from an arbitrary source. Squid uses a string search instead of parsing the Transfer-Encoding header to find chunked encoding. This allows an attacker to hide a second request inside Transfer-Encoding: it is interpreted by Squid as chunked and split out into a second request delivered upstream. Squid will then deliver two distinct responses to the client, corrupting any downstream caches.
How severe is CVE-2020-15811?
CVE-2020-15811 has a CVSS score of 6.5/10 (MEDIUM severity). The EPSS model estimates a 4.23% probability of exploitation in the next 30 days.
How do I fix CVE-2020-15811?
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-2020-15811?

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

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Source: NVD / NIST