HOMEVULNERABILITIESCVE-2020-5255
MEDIUM

CVE-2020-5255

CWE-435Published: March 30, 2020· Updated: Jun 17, 2026

4.3
CVSS v3.1

Official Description

In Symfony before versions 4.4.7 and 5.0.7, when a `Response` does not contain a `Content-Type` header, affected versions of Symfony can fallback to the format defined in the `Accept` header of the request, leading to a possible mismatch between the response's content and `Content-Type` header. When the response is cached, this can prevent the use of the website by other users. This has been patched in versions 4.4.7 and 5.0.7.

NVD Source

Technical Analysis

CVE-2020-5255 can be exploited remotely over the network without requiring physical or adjacent access, significantly expanding the attack surface for threat actors.

Exploitation requires low privileges, which limits the exposure to scenarios where an attacker has already gained initial access.

CVSS v3.1 Vector Breakdown

Exploitability
Attack VectorNetwork
Attack ComplexityLow
Privileges Req.Low
User InteractionNone
ScopeUnchanged
Impact
ConfidentialityNone
IntegrityNone
AvailabilityLow
CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:N/A:L

Affected Vendors & Products

sensiolabs1 product(s)
symfony
Source: NVD CPE · 1 total CPE entries

Exploit & PoC Resources

NO KNOWN EXPLOITNo public exploit confirmed at this time
Exploit-DB
Offensive Security exploit database
GitHub PoC Search
Community PoC repositories
Rapid7 / Metasploit
Metasploit module search
PacketStorm
Security advisories & exploits
NVD Detail
Official NIST entry
MITRE CVE
CVE Program entry
External links open in a new tab. Always verify in a controlled environment before use.

Official Patches & Advisories

PATCHhttps://github.com/symfony/symfony/commit/dca343442e6a954f96a2609e7b4e9c21ed6d74e6
PATCHhttps://github.com/symfony/symfony/commit/dca343442e6a954f96a2609e7b4e9c21ed6d74e6
ADVISORYhttps://github.com/symfony/symfony/security/advisories/GHSA-mcx4-f5f5-4859
ADVISORYhttps://symfony.com/blog/cve-2020-5255-prevent-cache-poisoning-via-a-response-content-type-header
ADVISORYhttps://github.com/symfony/symfony/security/advisories/GHSA-mcx4-f5f5-4859
ADVISORYhttps://symfony.com/blog/cve-2020-5255-prevent-cache-poisoning-via-a-response-content-type-header

All References (8)

→
https://github.com/symfony/symfony/commit/dca343442e6a954f96a2609e7b4e9c21ed6d74e6Patch · Third Party Advisory
→
https://github.com/symfony/symfony/security/advisories/GHSA-mcx4-f5f5-4859Third Party Advisory
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/C36JLPHUPKDFAX6D5WYFC4ALO2K7RDUQ/
→
https://symfony.com/blog/cve-2020-5255-prevent-cache-poisoning-via-a-response-content-type-headerThird Party Advisory
→
https://github.com/symfony/symfony/commit/dca343442e6a954f96a2609e7b4e9c21ed6d74e6Patch · Third Party Advisory
→
https://github.com/symfony/symfony/security/advisories/GHSA-mcx4-f5f5-4859Third Party Advisory
→
https://lists.fedoraproject.org/archives/list/package-announce%40lists.fedoraproject.org/message/C36JLPHUPKDFAX6D5WYFC4ALO2K7RDUQ/
→
https://symfony.com/blog/cve-2020-5255-prevent-cache-poisoning-via-a-response-content-type-headerThird Party Advisory

Quick Facts

CVE IDCVE-2020-5255
CVSS Score4.3 / 10
SeverityMEDIUM
WeaknessCWE-435
CISA KEVNo
Affected1 vendor(s)
PublishedMar 30, 2020

Related CVEs (CWE-435)

CVE-2021-34699
7.7
CVE-2023-43052
5.3

Recommended Actions

  • →Apply vendor patches immediately
  • →Monitor CVE-2020-5255 in threat intel feeds
  • →Review IDS/IPS signatures for exploitation attempts
Data sourced from NVD (NIST), CISA KEV, and EPSS (FIRST). Analysis generated by CTIWATCH.COM. CVE data is provided under the NVD usage policy.
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