httpc memory exhaustion via unbounded response header accumulation
Summary
| CVE | CVE-2026-55951 |
|---|---|
| State | PUBLISHED |
| Assigner | EEF |
| Source Priority | CVE Program / NVD first with legacy fallback |
| Published | 2026-09-01 15:17:20 UTC |
| Updated | 2026-09-08 01:17:50 UTC |
| Description | The Erlang/OTP httpc HTTP client does not enforce a limit on the total size of response headers received from a server. The max_header_size option defaults to nolimit, and httpc_response:parse_headers/6 accumulates every header into a list before the length check runs (which only fires after the terminating CRLF CRLF is received). A malicious or compromised HTTP server can send an arbitrarily large number of headers, or headers with very large values, causing the client process to allocate unbounded memory until the system runs out of memory or the BEAM VM crashes. A proof-of-concept server sending 100,000 headers of roughly 4000 bytes each caused the client VM to allocate over 13 GB of memory in under 30 seconds. Any application using httpc:request/4,5 to connect to untrusted servers is affected. No authentication is required: any server the client connects to (including via a redirect or man-in-the-middle) can trigger the exhaustion. This issue affects OTP from OTP 17.0 before OTP 27.3.4.17, from OTP 28.0 before OTP 28.5.0.6, and from OTP 29.0 before OTP 29.0.6, corresponding to inets from 5.10 before 9.3.2.7, from 9.4 before 9.6.2.3, and from 9.7 before 9.7.2. Whether OTP before OTP 17.0, corresponding to inets before 5.10, is affected is unknown. |
Risk And Classification
Primary CVSS: v4.0 8.2 HIGH from 6b3ad84c-e1a6-4bf7-a703-f496b71e49db
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
EPSS: 0.003820000 probability, percentile 0.312500000 (date 2026-09-03)
Problem Types: CWE-770 | CWE-770 CWE-770 Allocation of Resources Without Limits or Throttling
| Version | Source | Type | Score | Severity | Vector |
|---|---|---|---|---|---|
| 4.0 | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | Secondary | 8.2 | HIGH | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/C... |
| 4.0 | CNA | CVSS | 8.2 | HIGH | CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N |
CVSS v4.0 Breakdown
CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:N/VC:N/VI:N/VA:H/SC:N/SI:N/SA:N/E:X/CR:X/IR:X/AR:X/MAV:X/MAC:X/MAT:X/MPR:X/MUI:X/MVC:X/MVI:X/MVA:X/MSC:X/MSI:X/MSA:X/S:X/AU:X/R:X/V:X/RE:X/U:X
Vendor Declared Affected Products
| Source | Vendor | Product | Version | Platforms |
|---|---|---|---|---|
| CNA | Erlang | OTP | unknown 17.0 otp | Not specified |
| CNA | Erlang | OTP | affected 17.0 27.3.4.17 otp | Not specified |
| CNA | Erlang | OTP | affected 28.0 28.5.0.6 otp | Not specified |
| CNA | Erlang | OTP | affected 29.0 29.0.6 otp | Not specified |
| CNA | Erlang | OTP | unknown 5.10 otp | Not specified |
| CNA | Erlang | OTP | affected 5.10 9.3.2.7 otp | Not specified |
| CNA | Erlang | OTP | affected 9.4 9.6.2.3 otp | Not specified |
| CNA | Erlang | OTP | affected 9.7 9.7.2 otp | Not specified |
| CNA | Erlang | OTP | affected 84adefa331c4159d432d22840663c38f155cd4c1 * git | Not specified |
References
| Reference | Source | Link | Tags |
|---|---|---|---|
| github.com/erlang/otp/commit/e3be1cfe9f6cedd0cd20d9905e05601dfb31c8aa | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | github.com | |
| osv.dev/vulnerability/EEF-CVE-2026-55951 | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | osv.dev | |
| github.com/erlang/otp/security/advisories/GHSA-f9fw-mg7q-4g3x | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | github.com | |
| www.erlang.org/doc/system/versions.html | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | www.erlang.org | |
| github.com/erlang/otp/commit/aba0fe8c2d700bf4ac94607cf7f00e53bbe4042d | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | github.com | |
| cna.erlef.org/cves/CVE-2026-55951.html | 6b3ad84c-e1a6-4bf7-a703-f496b71e49db | cna.erlef.org | |
| CVE Program record | CVE.ORG | www.cve.org | canonical |
| NVD vulnerability detail | NVD | nvd.nist.gov | canonical, analysis |
Vendor Comments And Credit
Discovery Credit
CNA: Konrad Pietrzak / Ericsson (en)
Additional Advisory Data
Workarounds
CNA: * Restrict httpc to trusted servers only, and avoid using it to fetch resources from arbitrary or user-supplied URLs. * Apply operating-system memory limits (cgroups,ulimit) to contain the blast radius of a runaway client process. * Use an alternative HTTP client library that enforces a response header size limit.