Read the docs
TI-2026-33146 Aliases CVE-2026-45352

cpp-httplib DoS: Negative chunk-size in chunked Transfer-Encoding

Priority HIGH 72CWE-1285Published · Updated

Key facts

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

Attack profile from CVSS 3.1 · NVD. Fix status from CNA. Impact type from CWE-770.

Summary

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.43.4, negative chunk-size in chunked Transfer-Encoding causes unbounded memory allocation and process crash. The ChunkedDecoder::read_payload function in cpp-httplib (httplib.h) parses the chunk-size field of HTTP chunked transfer encoding using std::strtoul(). Per the C standard (§7.22.1.4), strtoul silently accepts a leading minus sign, performing unsigned wrap-around: strtoul("-2", …, 16) returns ULONG_MAX − 1 (0xFFFFFFFFFFFFFFFE). The library's only guard (line 12833) rejects ULONG_MAX (the result of "-1"), but any other negative value such as "-2" passes validation. The resulting near-maximum value is stored in chunk_remaining and controls how many bytes the server's read loop consumes from the network. This vulnerability is fixed in 0.43.4.

Why it matters now

Exploitation Proof of concept CISA SSVC · not in CISA KEV
EPSS 0.00327 25th percentileScored 2026-11-07
Public exploit Yes 1 exploit referenceTagged by NVD
Fix Fixed cpp-httplib (yhirose): 0.43.4

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 0.43.40.43.4Patch availableCNA
  • cpp-httplib Vendoryhirose Affected before 0.43.4 Fixed in 0.43.4 Patch available CNA

CPE configurations NVD · 1

CPEVersionsRoleVendor
cpe:2.3:a:yhirose:cpp-httplib:*:*:*:*:*:*:*:*before 0.43.4Vulnerableyhirose
  • cpe:2.3:a:yhirose:cpp-httplib:*:*:*:*:*:*:*:* Versions before 0.43.4 Vulnerable ·yhirose

Remediation

  • Fix · CNA cpp-httplib (yhirose) Fixed in 0.43.4

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-2026-45352

References

Exploit 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-2026-17313 cpp-httplib has CRLF injection in http headers CVSS 4.0HIGH 7.7
  • 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