CVE-2026-55603: http-proxy-middleware is node.js http-proxy middleware

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HIGH 7.5REMOTEUPGRADE

CVE-2026-55603 is a high-severity flaw (CVSS 7.5) affecting http-proxy-middleware. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

http-proxy-middleware is node.js http-proxy middleware. From 3.0.4 until 3.0.7 and 4.1.1, fixRequestBody() is the library's documented helper for re-emitting a request body that was already consumed by a body parser. When the outgoing Content-Type is multipart/form-data, it rebuilds the body with handlerFormDataBodyData(), which interpolates each req.body key and value directly into the multipart wire format without neutralizing CR/LF. A \r\n ins

Why this priority

High severity
Public exploit reference
Remotely exploitable, no login, no user action

A fixed release or distro patch exists.

Risk facts

CVSS score	7.5 (High)
Attack vector	Network (remote)
Attack complexity	High
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 79%)
CISA exploited list	No
Weakness	CWE-93
Published	2026-06-22
Last modified	2026-10-25

Publisher (CNA): GitHub, Inc. · Vendor: chimurai

Last updated 2026-10-25 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-06-22 21:16 UTCPublished CVE record published
2026-10-25 23:10 UTCUpdated Record last modified

chimurai http-proxy-middleware UPGRADE

Affected: >= 3.0.4 and < 3.0.7 · >= 4.0.0 and < 4.1.1

Fixed in: 3.0.7, 4.1.1

Safe to downgrade to: a release before 3.0.4

1. Check installed version

apt-cache policy http-proxy-middleware || rpm -q http-proxy-middleware || http-proxy-middleware --version

2. UPGRADE to 3.0.7 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade http-proxy-middleware

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade http-proxy-middleware

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 3.0.4 (Debian / Ubuntu)

apt-cache madison http-proxy-middleware sudo apt install http-proxy-middleware=<VERSION_BEFORE_3.0.4> sudo apt-mark hold http-proxy-middleware

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

dnf --showduplicates list http-proxy-middleware sudo dnf downgrade http-proxy-middleware-<VERSION_BEFORE_3.0.4> sudo dnf versionlock add http-proxy-middleware

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-2026-55603?

http-proxy-middleware: upgrade to 3.0.7, 4.1.1. Exact commands for each OS are on this page.

Is CVE-2026-55603 being exploited?

CVE-2026-55603 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-2026-55603 affect?

CVE-2026-55603 affects http-proxy-middleware. Severity is high (CVSS 7.5). http-proxy-middleware is node.js http-proxy middleware. From 3.0.4 until 3.0.7 and 4.1.1, fixRequestBody() is the library's documented helper for re-emitting a request body that was already consumed by a body parser. When the outgoing Conte

How urgent is CVE-2026-55603?

Priority 41/100. High severity; Public exploit reference; Remotely exploitable, no login, no user action

Software pages

Node.js vulnerabilities

Related CVEs

CVE-2026-55602 HIGH 8.6 UPGRADE http-proxy-middleware is node.js http-proxy middleware

References

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