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VulnerabilityPublished

CVE-2026-34441: yhirose cpp-httplib · HTTP Request/Response Smuggling

Affects yhirose cpp-httplibSource CVE Database V5

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Not known to be exploited · CVSS 4.8 Medium : upgrade to 0.40.0 when convenient.

Data as of 30 Oct 2026, 11:52 UTC

CVSS 3.1 base score
4.8Medium
How severe the flaw is on the 0–10 CVSS scale.
EPSS
0.2% chance of exploitation in 30 days – higher than 10% of CVEsExploit Prediction Scoring System: the likelihood attackers will use this flaw soon.
Patch
Available – fixed in 0.40.0
CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:L/I:L/A:N

Exploitation evidence

  1. Disclosed: evidence found.

    CVE published 31 Mar 2026

  2. Detectable: no evidence on record.

    No public nuclei template indexed

  3. Weaponized: no evidence on record.

    No public exploit code indexed in Metasploit or Exploit-DB

  4. Exploited in the wild: no evidence on record.

    Not in CISA KEV and no source reports exploitation

  5. Observed by OffSeq Mirage: no evidence on record.

    No attack traffic recorded by OffSeq Mirage sensors

A missing step is not evidence of safety. Sources: cve.org (opens in a new tab), the Metasploit, Exploit-DB and nuclei-templates index as of 30 Oct 2026.

What to do

Upgrade cpp-httplib and yhirose/cpp-httplib to 0.40.0.

Affected software

ProductAffectedFixed in
yhirosecpp-httplibAffected
  • <0.40.0
Fixed in
  • 0.40.0
GitHubyhirose/cpp-httplibpkg:github/yhirose/cpp-httplibOther threatsAffected
  • <0.40.0
Fixed in
  • 0.40.0

Check your own hosts for these packages with threat-finder (opens in a new tab), our free open-source scanner.

AI-suggested

This vulnerability has been patched in cpp-httplib version 0.40.0. Users should upgrade to version 0.40.0 or later to remediate this issue. No additional mitigation steps are indicated by the vendor advisory.

Description

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to version 0.40.0, cpp-httplib is vulnerable to HTTP Request Smuggling. The server's static file handler serves GET responses without consuming the request body. On HTTP/1.1 keep-alive connections, the unread body bytes remain on the TCP stream and are interpreted as the start of a new HTTP request. An attacker can embed an arbitrary HTTP request inside the body of a GET request, which the server processes as a separate request. This issue has been patched in version 0.40.0.

References

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