CVE-2020-5249

unknown

Published 2020-03-03 · Modified 2026-02-04

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CVSS v3

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

CVSS v4 NEW

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not yet in upstream

VIR risk

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Description

In Puma (RubyGem) before 4.3.3 and 3.12.4, if an application using Puma allows untrusted input in an early-hints header, an attacker can use a carriage return character to end the header and inject malicious content, such as additional headers or an entirely new response body. This vulnerability is known as HTTP Response Splitting. While not an attack in itself, response splitting is a vector for several other attacks, such as cross-site scripting (XSS). This is related to CVE-2020-5247, which fixed this vulnerability but only for regular responses. This has been fixed in 4.3.3 and 3.12.4.

Predictions

Exploit likelihood

30%

Patch ETA

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Heuristic predictions, AS-IS, for prioritization only.

Mitigations

No mitigations published for this CVE yet.

The vendor-content worker queues fetches as references arrive (check back in a few minutes). Or — if you've already worked around this in production — publish your fix to the community-verified tier.

✚ Propose a mitigation on Community → Mitigations published via the community go through AI scoring + 2 human reviewers + 7-day silent objection window before landing here with source_tier=community-verified.

OS impact

OS	Version	Status	Fixed in
debian	bookworm	fixed	`3.12.4-1`
debian	bullseye	fixed	`3.12.4-1`
debian	forky	fixed	`3.12.4-1`
debian	sid	fixed	`3.12.4-1`
debian	trixie	fixed	`3.12.4-1`

Package impact

Ecosystem	Package	Vulnerable	Fixed
RubyGems	puma	`<~> 3.12.4`	`~> 3.12.4`
RubyGems	puma	`<3.12.4`	`3.12.4`
RubyGems	puma	`>=4.0.0,<4.3.3`	`4.3.3`

References

Community-verified mitigations for this CVE will appear above when contributors publish them.

Verify integrity in audit chain (admin only). AS-IS.