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TI-2026-17313 Aliases CVE-2026-21428

cpp-httplib has CRLF injection in http headers

Priority HIGH 73CWE-93Published · Updated

Key facts

Attack vector
Network
Privileges required
None
User interaction
None
Attack complexity
Low
Attack requirements
None
Impact type
—
Confidentiality · integrity · availability
None · High · None
Fix status
Fixed

Attack profile from CVSS 4.0 · CNA. Fix status from CNA.

Summary

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to version 0.30.0, the ``write_headers`` function does not check for CR & LF characters in user supplied headers, allowing untrusted header value to escape header lines. This vulnerability allows attackers to add extra headers, modify request body unexpectedly & trigger an SSRF attack. When combined with a server that supports http1.1 pipelining (springboot, python twisted etc), this can be used for server side request forgery (SSRF). Version 0.30.0 fixes this issue.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00404 34th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed cpp-httplib (yhirose): 0.30.0

SSVC decision points

CISA ADP · SSVC 2.0.3

Exploitation
Poc
Automatable
Yes
Technical impact
Partial

The decision (Track, Attend, Act) also depends on your mission and well-being impact; see CISA's SSVC guide.

Affected products

VendorProductAffected versionsFixed inStatusSource
yhirosecpp-httplibbefore 0.30.00.30.0Patch availableCNA
  • cpp-httplib Vendoryhirose Affected before 0.30.0 Fixed in 0.30.0 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:yhirose:cpp-httplib:*:*:*:*:*:*:*:*before 0.30.0Vulnerableyhirose
  • cpe:2.3:a:yhirose:cpp-httplib:*:*:*:*:*:*:*:* Versions before 0.30.0 Vulnerable ·yhirose

Remediation

  • Fix · CNA cpp-httplib (yhirose) Fixed in 0.30.0

Vendor assessments

Red Hat

Red Hat's page for this CVE →

Not affected: 1 product
  • Red Hat

Timeline

  1. 2026-10-02 Threatist record created from CVE-2026-21428

References

Exploit 1

Patch 1

Other 1

  • TI-2026-33163 cpp-httplib: HTTP header value percent-decoding in server-side `parse_header` enables CRLF injection CVSS 3.1CRITICAL 9.9
  • TI-2026-18294 cpp-httplib vulnerable to a denial of service (DOS) using a zip bomb CVSS 4.0HIGH 8.7
  • TI-2026-33146 cpp-httplib DoS: Negative chunk-size in chunked Transfer-Encoding CVSS 3.1HIGH 7.5
  • TI-2026-22709 Uncontrolled resource consumption in yhirose cpp-httplib CVSS 3.1HIGH 7.5
  • TI-2025-33556 cpp-httplib Unbounded Memory Allocation in Chunked/No-Length Requests Vulnerability CVSS 3.1HIGH 7.5
  • TI-2025-32923 cpp-httplib has unlimited number of http header fields, which causes memory leak CVSS 3.1HIGH 7.5
See all 19 →

Sources

This product uses the NVD API but is not endorsed or certified by the NVD. Sources and licences