CVE-2026-31870 | cpp-httplib Affected by Remote Process Crash via Malformed Content-Length Response Header

Exp

cpp-httplib is a C++11 single-file header-only cross platform HTTP/HTTPS library. Prior to 0.37.1, when a cpp-httplib client uses the streaming API (httplib::stream::Get, httplib::stream::Post, etc.), the library calls std::stoull() directly on the Content-Length header value received from the server with no input validation and no exception handling. std::stoull throws std::invalid_argument for non-numeric strings and std::out_of_range for values exceeding ULLONG_MAX. Since nothing catches these exceptions, the C++ runtime calls std::terminate(), which kills the process with SIGABRT. Any server the client connects to — including servers reached via HTTP redirects, third-party APIs, or man-in-the-middle positions can crash the client application with a single HTTP response. No authentication is required. No interaction from the end user is required. The crash is deterministic and immediate. This vulnerability is fixed in 0.37.1.

Published: 2026-03-11 Last update: 2026-03-18 Assigner: [email protected] Source: [email protected]
NVD Status：Analyzed，CVE State: published
View at NVD, CVE.org, EUVD

CVE-2026-31870 is rated Exploit Available (51.8/100): CVSS High severity, with low exploitation likelihood (EPSS 0.06%). 1 public exploit reference(s) are indexed (Exploit-DB). Public exploits are available—assess exposure, apply mitigations, and prioritize patching.

Risk is dynamic; we continuously reassess and refresh what is shown on this page as upstream context changes.

Public exploit references (Exploit-DB) for CVE-2026-31870

EDB-ID Source Kind Published Link
— nvd_ref exploit_tag Exploit-DB ↗

Exploit prediction scoring system (EPSS) score for CVE-2026-31870

EPSS lead: Daily EPSS estimates relative likelihood of exploitation; percentile ranks this CVE among scored vulnerabilities (higher = more severe relative rank).

# Date Old EPSS score New EPSS score Delta (New - Old)
1 2026-03-12 — 0.06% —

Full EPSS history (1 record total)

Common vulnerability scoring system (CVSS) metrics for CVE-2026-31870

CVSS metrics for this CVE.

Base score Version Severity Vector Exploitability Impact Score source
7.5 3.1 HIGH
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:N/A:H Click to expand
Attack vector (AV:N)
Could be attacked over the internet or any normal routed network—not just someone sitting at the machine.
Attack complexity (AC:L)
Once they can reach the bug, pulling it off is straightforward—no weird race conditions or rare setup.
Privileges required (PR:N)
No account or special rights needed—anonymous or random user is enough.
User interaction (UI:N)
Nobody has to click “OK” or open a trap file; it can work without a victim helping.
Scope (S:U)
Damage stays in the same “trust bubble” as the broken component—no big spill into unrelated systems.
Confidentiality (C:N)
Doesn’t really leak secrets in a meaningful way.
Integrity (I:N)
Data isn’t meaningfully altered or forged.
Availability (A:H)
Could take the service down hard or make it unusable for people who depend on it.
 3.9 3.6 [email protected]

Weakness enumeration for CVE-2026-31870

OS Trackers for CVE-2026-31870

vendor priority summary link
debian not yet assigned CVE-2026-31870 not yet assigned priority: Debian including 1 source packages (cpp-httplib), 4 status rows across 4 suites (bookworm, forky, sid, trixie): open 2, resolved 2. https://security-tracker.debian.org/tracker/CVE-2026-31870
redhat high — https://access.redhat.com/security/cve/CVE-2026-31870
suse high CVE-2026-31870 severity important: SUSE including 2 source package names (cpp-httplib, libcpp-httplib0_22), 4 product×package rows across 2 product lines (SUSE Linux Enterprise Server 16.0, SUSE Linux Enterprise Server for SAP applications 16.0): Known Not Affected 4. https://www.suse.com/security/cve/CVE-2026-31870/
ubuntu medium CVE-2026-31870 medium priority: Ubuntu including 1 source packages (cpp-httplib), 4 status rows across 4 suites (jammy, noble, questing, upstream): needs-triage 4. https://ubuntu.com/security/CVE-2026-31870

Affected software / configurations for CVE-2026-31870

Vendor Product Version Raw CPE
yhirose cpp-httplib < 0.37.1 cpe:2.3:a:yhirose:cpp-httplib:*:*:*:*:*:*:*:*

References for CVE-2026-31870

cvelogic Threat Intelligence