CVE-2026-49756: Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in wojtekmach Req allows multipart

Routine

LOW 3.7REMOTEUPGRADE

CVE-2026-49756 is a low-severity flaw (CVSS 3.7) affecting req. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in wojtekmach Req allows multipart parameter smuggling via attacker-influenced part metadata. Req.Utils.encode_form_part/2 in lib/req/utils.ex builds the per-part headers by interpolating the caller-supplied name, filename, and content_type values directly into the content-disposition and content-type lines with no escaping or CRLF stripping. A value containing ", \r, or

Why this priority

Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	3.7 (Low)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.2% (top 89%)
CISA exploited list	No
Weakness	CWE-93
Published	2026-06-08
Last modified	2026-08-18

Publisher (CNA): EEF · Vendor: wojtekmach

Last updated 2026-08-18 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-08 16:16 UTCPublished CVE record published
2026-08-18 19:15 UTCUpdated Record last modified

wojtekmach req UPGRADE

Affected: >= 0.5.3 and < 0.6.0

Fixed in: 0.6.0

Safe to downgrade to: a release before 0.5.3

1. Check installed version

apt-cache policy req || rpm -q req || req --version

2. UPGRADE to 0.6.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade req

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade req

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

3. If no update is available yet, DOWNGRADE to a release before 0.5.3 (Debian / Ubuntu)

apt-cache madison req sudo apt install req=<VERSION_BEFORE_0.5.3> sudo apt-mark hold req

3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list req sudo dnf downgrade req-<VERSION_BEFORE_0.5.3> sudo dnf versionlock add req

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2026-49756?

req: upgrade to 0.6.0. Exact commands for each OS are on this page.

Is CVE-2026-49756 being exploited?

CVE-2026-49756 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2026-49756 affect?

CVE-2026-49756 affects req. Severity is low (CVSS 3.7). Improper Neutralization of CRLF Sequences ('CRLF Injection') vulnerability in wojtekmach Req allows multipart parameter smuggling via attacker-influenced part metadata. Req.Utils.encode_form_part/2 in lib/req/utils.ex builds the per-part h

How urgent is CVE-2026-49756?

Priority 21/100. Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-49755 HIGH 7.5 UPGRADE Improper Handling of Highly Compressed Data (Data Amplification) vulnerability in wojtekmach Req allows attack

References

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