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CVE-2025-46728

cpp-httplib has Unbounded Memory Allocation in Chunked/No-Length Requests

7.5 HighFix available

cpp-httplib is a C++ header-only HTTP/HTTPS server and client library. Prior to version 0.20.1, the library fails to enforce configured size limits on incoming request bodies when Transfer-Encoding: chunked is used or when no Content-Length header is provided. A remote attacker can send a chunked request without the terminating zero-length chunk, causing uncontrolled memory allocation on the server. This leads to potential exhaustion of system memory and results in a server crash or unresponsiveness. Version 0.20.1 fixes the issue by enforcing limits during parsing. If the limit is exceeded at any point during reading, the connection is terminated immediately. A short-term workaround through a Reverse Proxy is available. If updating the library immediately is not feasible, deploy a reverse proxy (e.g., Nginx, HAProxy) in front of the cpp-httplib application. Configure the proxy to enforce maximum request body size limits, thereby stopping excessively large requests before they reach the vulnerable library code.

Attack profile

How easy it is to exploit

Attack vector
Network
Complexity
Low
Privileges needed
None
User interaction
None

What an attacker can affect

Confidentiality
None
Integrity
None
Availability
High

Exploit likelihood

0.68%Up 0.5 points since May 6, 2025
90%50%10%1%

What each source reports

CVE List Score used 7.5

cpp-httplib has Unbounded Memory Allocation in Chunked/No-Length Requests

cpp-httplib is a C++ header-only HTTP/HTTPS server and client library. Prior to version 0.20.1, the library fails to enforce configured size limits on incoming request bodies when Transfer-Encoding: chunked is used or when no Content-Length header is provided. A remote attacker can send a chunked request without the terminating zero-length chunk, causing uncontrolled memory allocation on the server. This leads to potential exhaustion of system memory and results in a server crash or unresponsiveness. Version 0.20.1 fixes the issue by enforcing limits during parsing. If the limit is exceeded at any point during reading, the connection is terminated immediately. A short-term workaround through a Reverse Proxy is available. If updating the library immediately is not feasible, deploy a reverse proxy (e.g., Nginx, HAProxy) in front of the cpp-httplib application. Configure the proxy to enforce maximum request body size limits, thereby stopping excessively large requests before they reach the vulnerable library code.

Record
CVE-2025-46728
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400
Updated
2026-11-02
EUVDEUVD-2025-13496 7.5

cpp-httplib is a C++ header-only HTTP/HTTPS server and client library. Prior to version 0.20.1, the library fails to enforce configured size limits on incoming request bodies when Transfer-Encoding: chunked is used or when no Content-Length header is provided. A remote attacker can send a chunked request without the terminating zero-length chunk, causing uncontrolled memory allocation on the server. This leads to potential exhaustion of system memory and results in a server crash or unresponsiveness. Version 0.20.1 fixes the issue by enforcing limits during parsing. If the limit is exceeded at any point during reading, the connection is terminated immediately. A short-term workaround through a Reverse Proxy is available. If updating the library immediately is not feasible, deploy a reverse proxy (e.g., Nginx, HAProxy) in front of the cpp-httplib application. Configure the proxy to enforce maximum request body size limits, thereby stopping excessively large requests before they reach the vulnerable library code.

Record
EUVD-2025-13496
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
NVD 7.5

cpp-httplib is a C++ header-only HTTP/HTTPS server and client library. Prior to version 0.20.1, the library fails to enforce configured size limits on incoming request bodies when Transfer-Encoding: chunked is used or when no Content-Length header is provided. A remote attacker can send a chunked request without the terminating zero-length chunk, causing uncontrolled memory allocation on the server. This leads to potential exhaustion of system memory and results in a server crash or unresponsiveness. Version 0.20.1 fixes the issue by enforcing limits during parsing. If the limit is exceeded at any point during reading, the connection is terminated immediately. A short-term workaround through a Reverse Proxy is available. If updating the library immediately is not feasible, deploy a reverse proxy (e.g., Nginx, HAProxy) in front of the cpp-httplib application. Configure the proxy to enforce maximum request body size limits, thereby stopping excessively large requests before they reach the vulnerable library code.

Record
CVE-2025-46728
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400
Updated
2026-11-02
OSV 7.5

cpp-httplib has Unbounded Memory Allocation in Chunked/No-Length Requests

cpp-httplib is a C++ header-only HTTP/HTTPS server and client library. Prior to version 0.20.1, the library fails to enforce configured size limits on incoming request bodies when Transfer-Encoding: chunked is used or when no Content-Length header is provided. A remote attacker can send a chunked request without the terminating zero-length chunk, causing uncontrolled memory allocation on the server. This leads to potential exhaustion of system memory and results in a server crash or unresponsiveness. Version 0.20.1 fixes the issue by enforcing limits during parsing. If the limit is exceeded at any point during reading, the connection is terminated immediately. A short-term workaround through a Reverse Proxy is available. If updating the library immediately is not feasible, deploy a reverse proxy (e.g., Nginx, HAProxy) in front of the cpp-httplib application. Configure the proxy to enforce maximum request body size limits, thereby stopping excessively large requests before they reach the vulnerable library code.

Record
CVE-2025-46728
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Weakness
CWE-400
Updated
2026-11-02
OSVDEBIAN-CVE-2025-46728 7.5

cpp-httplib is a C++ header-only HTTP/HTTPS server and client library. Prior to version 0.20.1, the library fails to enforce configured size limits on incoming request bodies when Transfer-Encoding: chunked is used or when no Content-Length header is provided. A remote attacker can send a chunked request without the terminating zero-length chunk, causing uncontrolled memory allocation on the server. This leads to potential exhaustion of system memory and results in a server crash or unresponsiveness. Version 0.20.1 fixes the issue by enforcing limits during parsing. If the limit is exceeded at any point during reading, the connection is terminated immediately. A short-term workaround through a Reverse Proxy is available. If updating the library immediately is not feasible, deploy a reverse proxy (e.g., Nginx, HAProxy) in front of the cpp-httplib application. Configure the proxy to enforce maximum request body size limits, thereby stopping excessively large requests before they reach the vulnerable library code.

Record
DEBIAN-CVE-2025-46728
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVOESA-2025-1610 7.5

cpp-httplib security update

A C++11 single-file header-only cross platform HTTP/HTTPS library. It's extremely easy to setup. Just include httplib.h file in your code!

Security Fix(es):

cpp-httplib is a C++ header-only HTTP/HTTPS server and client library. Prior to version 0.20.1, the library fails to enforce configured size limits on incoming request bodies when Transfer-Encoding: chunked is used or when no Content-Length header is provided. A remote attacker can send a chunked request without the terminating zero-length chunk, causing uncontrolled memory allocation on the server. This leads to potential exhaustion of system memory and results in a server crash or unresponsiveness. Version 0.20.1 fixes the issue by enforcing limits during parsing. If the limit is exceeded at any point during reading, the connection is terminated immediately. A short-term workaround through a Reverse Proxy is available. If updating the library immediately is not feasible, deploy a reverse proxy (e.g., Nginx, HAProxy) in front of the cpp-httplib application. Configure the proxy to enforce maximum request body size limits, thereby stopping excessively large requests before they reach the vulnerable library code.(CVE-2025-46728)

Record
OESA-2025-1610
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
Show 5 moreShow less
OSVOESA-2025-1611 7.5

cpp-httplib security update

A C++11 single-file header-only cross platform HTTP/HTTPS library. It's extremely easy to setup. Just include httplib.h file in your code!

Security Fix(es):

cpp-httplib is a C++ header-only HTTP/HTTPS server and client library. Prior to version 0.20.1, the library fails to enforce configured size limits on incoming request bodies when Transfer-Encoding: chunked is used or when no Content-Length header is provided. A remote attacker can send a chunked request without the terminating zero-length chunk, causing uncontrolled memory allocation on the server. This leads to potential exhaustion of system memory and results in a server crash or unresponsiveness. Version 0.20.1 fixes the issue by enforcing limits during parsing. If the limit is exceeded at any point during reading, the connection is terminated immediately. A short-term workaround through a Reverse Proxy is available. If updating the library immediately is not feasible, deploy a reverse proxy (e.g., Nginx, HAProxy) in front of the cpp-httplib application. Configure the proxy to enforce maximum request body size limits, thereby stopping excessively large requests before they reach the vulnerable library code.(CVE-2025-46728)

Record
OESA-2025-1611
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVOESA-2025-1612 7.5

cpp-httplib security update

A C++11 single-file header-only cross platform HTTP/HTTPS library. It's extremely easy to setup. Just include httplib.h file in your code!

Security Fix(es):

cpp-httplib is a C++ header-only HTTP/HTTPS server and client library. Prior to version 0.20.1, the library fails to enforce configured size limits on incoming request bodies when Transfer-Encoding: chunked is used or when no Content-Length header is provided. A remote attacker can send a chunked request without the terminating zero-length chunk, causing uncontrolled memory allocation on the server. This leads to potential exhaustion of system memory and results in a server crash or unresponsiveness. Version 0.20.1 fixes the issue by enforcing limits during parsing. If the limit is exceeded at any point during reading, the connection is terminated immediately. A short-term workaround through a Reverse Proxy is available. If updating the library immediately is not feasible, deploy a reverse proxy (e.g., Nginx, HAProxy) in front of the cpp-httplib application. Configure the proxy to enforce maximum request body size limits, thereby stopping excessively large requests before they reach the vulnerable library code.(CVE-2025-46728)

Record
OESA-2025-1612
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVOESA-2025-1613 7.5

cpp-httplib security update

A C++11 single-file header-only cross platform HTTP/HTTPS library. It's extremely easy to setup. Just include httplib.h file in your code!

Security Fix(es):

cpp-httplib is a C++ header-only HTTP/HTTPS server and client library. Prior to version 0.20.1, the library fails to enforce configured size limits on incoming request bodies when Transfer-Encoding: chunked is used or when no Content-Length header is provided. A remote attacker can send a chunked request without the terminating zero-length chunk, causing uncontrolled memory allocation on the server. This leads to potential exhaustion of system memory and results in a server crash or unresponsiveness. Version 0.20.1 fixes the issue by enforcing limits during parsing. If the limit is exceeded at any point during reading, the connection is terminated immediately. A short-term workaround through a Reverse Proxy is available. If updating the library immediately is not feasible, deploy a reverse proxy (e.g., Nginx, HAProxy) in front of the cpp-httplib application. Configure the proxy to enforce maximum request body size limits, thereby stopping excessively large requests before they reach the vulnerable library code.(CVE-2025-46728)

Record
OESA-2025-1613
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVUBUNTU-CVE-2025-46728 7.5

cpp-httplib is a C++ header-only HTTP/HTTPS server and client library. Prior to version 0.20.1, the library fails to enforce configured size limits on incoming request bodies when Transfer-Encoding: chunked is used or when no Content-Length header is provided. A remote attacker can send a chunked request without the terminating zero-length chunk, causing uncontrolled memory allocation on the server. This leads to potential exhaustion of system memory and results in a server crash or unresponsiveness. Version 0.20.1 fixes the issue by enforcing limits during parsing. If the limit is exceeded at any point during reading, the connection is terminated immediately. A short-term workaround through a Reverse Proxy is available. If updating the library immediately is not feasible, deploy a reverse proxy (e.g., Nginx, HAProxy) in front of the cpp-httplib application. Configure the proxy to enforce maximum request body size limits, thereby stopping excessively large requests before they reach the vulnerable library code.

Record
UBUNTU-CVE-2025-46728
CVSS 3.1
7.5 HighCVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H
Updated
2026-11-02
OSVopenSUSE-SU-2025:15084-1 No score

cpp-httplib-devel-0.20.1-1.1 on GA media

These are all security issues fixed in the cpp-httplib-devel-0.20.1-1.1 package on the GA media of openSUSE Tumbleweed.

Record
openSUSE-SU-2025:15084-1
Updated
2026-11-02

Affected products

Affected packages

Affected packages
PackageAffectedFixed
cpp-httplib
Debian:12
All versions, plus listed versions
0.11.4+ds-10.11.4+ds-1+deb12u10.11.4+ds-20.11.4+ds-30.13.1+ds-1
Show 22 moreShow less
0.14.0+ds-10.14.1+ds-10.14.1+ds-20.14.2+ds-10.14.3+ds-10.14.3+ds-1.10.14.3+ds-1.1~exp10.15.3+ds-10.15.3+ds-20.15.3+ds-30.16.0+ds-10.16.3+ds-10.16.3+ds-20.18.0+ds-10.18.7-10.20.1+ds-30.25.0+ds-10.26.0+ds-20.41.0+ds-10.41.0+ds-20.41.0+ds-30.41.0+ds-3~bpo13+1
None known
cpp-httplib
Debian:13
before 0.18.7-1+deb13u1, plus listed versions
0.18.7-1
0.18.7-1+deb13u1
cpp-httplib
Debian:14
before 0.25.0+ds-3, plus listed versions
0.18.7-10.20.1+ds-30.25.0+ds-1
0.25.0+ds-3
cpp-httplib
openEuler:22.03-LTS-SP4
before 0.12.4-4.oe2203sp4
0.12.4-4.oe2203sp4
cpp-httplib
openEuler:24.03-LTS
before 0.14.0-4.oe2403
0.14.0-4.oe2403
cpp-httplib
openEuler:24.03-LTS-SP1
before 0.14.0-4.oe2403sp1
0.14.0-4.oe2403sp1
cpp-httplib
openEuler:22.03-LTS-SP3
before 0.12.4-4.oe2203sp3
0.12.4-4.oe2203sp3
cpp-httplib
Ubuntu:Pro:22.04:LTS
All versions, plus listed versions
0.9.9+ds-10.9.10+ds-10.10.1+ds-10.10.2+ds-10.10.3+ds-10.10.3+ds-1ubuntu0.1~esm10.10.3+ds-1ubuntu0.1~esm2
None known
cpp-httplib
Ubuntu:Pro:24.04:LTS
All versions, plus listed versions
0.13.1+ds-1ubuntu10.14.3+ds-10.14.3+ds-1.10.14.3+ds-1.1build10.14.3+ds-1.1build20.14.3+ds-1.1ubuntu0.1~esm10.14.3+ds-1.1ubuntu0.1~esm2
None known
cpp-httplib
Ubuntu:25.10
All versions, plus listed versions
0.18.7-10.18.7-1ubuntu0.25.10.10.18.7-1ubuntu0.25.10.2
None known
cpp-httplib
Ubuntu:Pro:26.04:LTS
All versions, plus listed versions
0.18.7-10.26.0+ds-2ubuntu20.26.0+ds-2ubuntu30.26.0+ds-2ubuntu3+esm1
None known
cpp-httplib
openSUSE:Tumbleweed
before 0.20.1-1.1
0.20.1-1.1

History

History
RecordedChangedSources
first indexedCVE List, EUVD, NVD, OSV

Dates are when Every CVE recorded each change. Upstream dates may differ.

In short

CVE-2025-46728 is a high vulnerability (CVSS 7.5) in Cpp-httplib Project Cpp-httplib, published May 6, 2025. No source lists public exploit code. EPSS puts the chance of exploitation in the next 30 days at 0.68%, the 52nd percentile. Fixed in cpp-httplib 0.18.7-1+deb13u1.

References

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