CVE-2026-45372: cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library

Q: How do I fix CVE-2026-45372?

cpp-httplib: upgrade to 0.44.0. Exact commands for each OS are on this page.

Q: Is CVE-2026-45372 being exploited?

CVE-2026-45372 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2026-45372 affect?

CVE-2026-45372 affects cpp-httplib. Severity is critical (CVSS 9.9). cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, when cpp-httplib's server parses an incoming request, it applies percent-decoding to every header value except Location and Referer. The vali

Q: How urgent is CVE-2026-45372?

Priority 50/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

This week

CRITICAL 9.9REMOTEUPGRADE

CVE-2026-45372 is a critical-severity flaw (CVSS 9.9) affecting cpp-httplib. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, when cpp-httplib's server parses an incoming request, it applies percent-decoding to every header value except Location and Referer. The validity check (is_field_value) is run before decoding, so encoded %0D%0A passes the check and is then expanded to a literal \r\n byte pair inside the stored header value. This vulnerability is fixed in 0.44.0.

Why this priority

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

A fixed release or distro patch exists.

Risk facts

CVSS score	9.9 (Critical)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	None
EPSS exploit chance	0.3% (top 78%)
CISA exploited list	No
Weakness	CWE-93, CWE-444
Published	2026-05-29
Last modified	2026-07-22

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

Last updated 2026-07-22 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2026-05-29 20:16 UTCPublished CVE record published
2026-07-22 06:10 UTCUpdated Record last modified

yhirose cpp-httplib UPGRADE

Affected: < 0.44.0

Fixed in: 0.44.0

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy cpp-httplib || rpm -q cpp-httplib || cpp-httplib --version

2. UPGRADE to 0.44.0 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade cpp-httplib

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade cpp-httplib

Note

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

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-2026-45372?

cpp-httplib: upgrade to 0.44.0. Exact commands for each OS are on this page.

Is CVE-2026-45372 being exploited?

CVE-2026-45372 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-2026-45372 affect?

CVE-2026-45372 affects cpp-httplib. Severity is critical (CVSS 9.9). cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.44.0, when cpp-httplib's server parses an incoming request, it applies percent-decoding to every header value except Location and Referer. The vali

How urgent is CVE-2026-45372?

Priority 50/100. Critical severity; Public exploit reference; Remotely exploitable, no login, no user action

Related CVEs

CVE-2026-54919 HIGH 7.4 UPGRADE cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library
CVE-2026-46527 HIGH 7.5 UPGRADE cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library
CVE-2026-45352 MEDIUM 5.3 UPGRADE cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library

References

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